I don't know how prices run where you are located... But here in VA ,I'd have to say your "trusted" mechanic is taking you for a ride.If you aren't comfortable w/ the timing & valve cover gaskets, look up the parts required on-line;print them off w/ prices & ask why the labor is so high. Check w/ some other shops.....you may trust this guy, but you don't have to sleep w/ him .Items 2,4,5,&6 you can do yourself if you have some mechanical ability. Maybe this link will help. http://www.mitsubishilinks.com/ They are shop manuals.

Va_Stumpy
89 Raider
"Never judge horsepower by exhaust"
3.0
automatic
stock as a rock
Dual Bouncy Seats