Audi A4 1.8 Quatro 2003 B6-multiple problems!

[Myst]

On Monday, the coolant light came on...we planned to top it off and then flush it over the weekend...car overheated Wednesday...had it towed home...topped the coolant off and drove to dealer-spent $1200 at dealer on flange, tempsender, thermostat & 2 vacuum valves (brake system)-dealer also stated that coil in cyl 2 was bad-for the price being charged decided I would do it myself and replace all 4-switched coil pack 2 with 3 and 2 continued to have the misfires-ran fault codes before buying and now getting 17705, 17951, 17580, 17987, 16497 & 16685 along with the misfire codes. These faults were not there when checked on 9/10 or 9/12 (after bringing home)...they just started this morning. We did the throttle body alignment, and it did not help. We have also checked every hose and cannot find a broken one. We also thought maybe we should change the air filter but it appears it will take forever to get the old one out. If we change the coils, will that fix all of these problems or is there something else going on?

Thank you for any advice!

[Myst]

Update...put in the new plugs, coil packs and a pressure relief vent. Car does not shudder as much and seems to stay steady at 900...at least it stays running now. BUT, (I have forgotten if I mentioned this in the original post) the oil all over the engine and the inside of the hood has come back. When we brought the car back from the dealer we noticed oil everywhere...assumed the techs just did not push the dipstick down all the way. We pressure washed the engine before putting in the plugs, etc, and everything seemed fine...no oil spewing or dripping. We ran the car in the driveway with no issues, then decided to take it out for a test drive. We drove about 7 miles to our destination, popped the hood and the oil was everywhere again...any ideas where this could be coming from? When the car originally overheated and we took it to the dealer, we did not have any oil issues.