My wifes 2000 GXE

I bought my wife a brand new 2000 GXE in November of 2000. I didn't worry about a break in period, we weren't hard on it, but I did take it for a short cruise on the highway staying around 65 MPH. Well, anyway... When the car hit 3000 miles I told my wife to take the car for an oil change. The stupid car salesman forgot to mail me the free oil change coupons, and the dealership is a bit of a drive so I told my wife to take it to a local shop. She took it to a shop my mother-in-law adores for some strange reason. They changed the oil w/ Castrol Syntec 10W-30. A few days later she came home and I smelled burning oil. It was dark out and as I walked toward the car I could see smoke in the moonlight! I checked the oil and it was about an INCH over the hot mark on the dipstick. I went to the shop first thing in the morning and waited for them to drain it. What should have been a 10 minute wait took 2 hours and the mechanic still had the car on the lift, walked over to me and showed me the dipstick. It looked normal. He then said that it was only a half quart high. I thought yeah right, I figured he was just trying to cover his ***. I was in a hury so I jeted to work and didn't bother to check it. That was about 100 miles after the oil was changed. About a week later I was driving my wifes car again and after I got off the highway the car had no power and smoke poured out the exhaust! I checked the oil and it was still where it was when I took the damn thing to the shop. I was pissed. I took the car to the shop and showed the owner. Another mechanic drained off 4 1/2 quarts of oil. I started yelling like a maniac. I told them the car only held 2 7/8 quarts when the filter was changed and 2 5/8 w/o the filter changed. They didn't believe me so I showed them the wonderfull sticker under the hood that showed oil capacity, etc. And then I showed them the manual. The mechanic originally put in 5 quarts of oil! What made me so mad was that I took it up there, he put it on the rack and didn't even bother to drain it all off! I saw him pull the plug and drain off oil, and then start the engine. He kept checking it. He smarted off and said that the smoke was just oil being burned out the vent. Duh! If you add twice the amount of oil the car holds you'll burn oil! I know the car had blow-by. I'm sure that most of the smoke was oil that had passed throught the PCV valve and breather filters and into the intake. I don't think (and hope) that it did too much damage on the seals. I called the dealer and told them. They said that it wasn't a warranty issue. I called back and talked to the owner of the dealer. He agreed to evaluate the car and run a dyno test with no charge. If there was damage the owner of the shop agreed to pay, in writing. I didn't want to drive the car to the dealer. When I would start the car (after sitting 2 days) all the gunked up half burnt oil had made a couple of exhaust valves stick open and the push rods were taping them real hard. The owner of the shop agreed to have the car towed to the dealer. They were supposed to pick the car up at 8am, they were there at 9:30am. I called the dealer when I got to work. They didn't have the car yet. Called at lunch. Still no car. Finally at 3pm the dealer called and said the car had just arrived! They wanted the car to sit overnight so they could do the tests in the morning when it was cold, so they could run it in the same conditions I was. I called the owner of the shop and raised hell b/c he had my car for 6 hours. He asured me that nothing was done. I assured him that he was about to get a foot in his ***, along with a summons to claims court. The dealer called me the next day at work. They said the car didn't smoke at all, and that they dyno tests looked fine. I had them check all the o2 sensors and the cat. All ok. I'm taking the car to another dealer so he can evaluate it, I don't trust the first dealers tests. I think the shop owner had the tow truck bring the car to the shop and they ran some detergent into the throttle body, to clean off all of the carboned up oil that was making it smoke and hesitate. The night before the car went to the dealer, it sounded like crap and smoked like a crazy. Here it is 2 months later, ready for 2nd oil change. Ran the piss out of the car on the highway. I only have my wife run 93 octane gas, and 104+ every few tanks. Seems like the car got its balls back. Peppy again w/ no hesitation. Anyone got any ideas as to how to approach this? Any recources to turn to or any ideas as to what could have been damaged. The dealer said that everything here on out will be covered under nissans warranty, even the problems related to the overfilling of oil. I hope that the oil just gunked up the exhaust valves and now its burnt off. I've called a lawyer, and they're too expensive, and the Better Business Burea. Anybody got any ideas other than the obvious, which is beat the crap out of the mechanic and make him drink 5 quarts of oil? Perhaps some cheap tricks to ensure that the car will run clean and strong for its life? Thanks. BTW, come to find out that my mother-in-law had these morons at this shop install a new tranny in her tarus. They had installed 3 trannys and they all failed within a couple months of each other. Nothing like a mechanic who got his ASE certification out of cracker jack box.