Ok.. others please toss in ideas as well...I'm going on what I do and know.
You will need 3/8 drive metric sockets and a nice ratchet.
I've found that if you buy 6 point sockets instead of 12 point you will only be happier in the long run. They grip and hold better because there'* more surface turning the bolt.
Basic 3/8 extensions. like a 3", 6" and 12"
From Sears I picked up a flexible head ratchet. It'* not for everyone but it makes those odd angles easy to deal with...you just bend the head at the pivot point and go to town.
Your basic screwdriver set. Small screw driver or a pick is a must for some of the tabs on connectors. You don't pry the connector..just use the driver/pick to lift the tab on the connector.
A torque wrench. Again..Sears .. the one that clicks. Read the directions to ensure you use it properly.
Gasket scraper is always nice.
3 or so cans of brake clean. It is the best for cleaning oil and other residues off mating surfaces where a gasket is going to be.
Needle nose pliers.
And no doubt the best tool in the world when you need it. A magnetic pickup tool. (usually looks like an old radio antenna) Sears
Some of these things you can get at lower cost places. We have a place called Ocean State Job Lot here... pliers, needle nose, magnetic pick up tool, pick set... I'd buy most of that there.
Things like the sockets and torque wrench..you'll have forever...don't overspend..but buy quality.. like a craftsman with lifetime warranty. Anything happens and you walk back in, they hand you a new one.
Some will call me things. I picked up some gloves..like surgeons use from my local parts place. They sorts suck in the hot weather but keep you much cleaner. Having a desk job I don't want to come in w/grease embedded hands.
Some rags and things to catch fluids.
00 Regal GS: All kinds of cool stuff.