Like Nick suggested, buy a set of 1/4" drive sockets and don't use harbor freight stuff. Craftsman is still decent tools. Snap-On is great, but not worth it if you aren't making a living with 'em. As Tim Allen says......"I've got tools to FIX tools!" YOu just can't have enough tools in a tool box. $500 will get you "started" If you want a list of tools that are a must for a turbo Buick owner, I can post what I feel is a must. It'd take a bit of thinking.
The turbo mounting bracket bolts are 13mm head size and are 10mm x 1.5 thread size. I use a long wrench on the upper one and a 13mm wobbly socket on a 12" extension (3/8" drive) on the lower. You don't need a whole wobbly set. 10mm, 13mm, 15mm will get you there.
Buy every kind of socket Sears has in 8mm, 10mm, 13mm, 15mm. (1/4" drive, 3/8" drive) Same with wrenches, but add 17mm, 18mm. Buy Gear Wrench sets also. BIG flat blade screwdriver (great pry bar) complete screw driver sets, slip joint pliers, dykes (or to be politically correct......"alternative lifestyle cutters") or wire cutters in mini and normal sizes, channel lock pliers, assorted Vise Grips, complete SAE sockets for engine work, hammers (to hit the wall with when things don't go right) Power Probe electrical tester
http://www.amazon.com/Power-Probe-219FT-Circuit-Tester/dp/B000KPU8JI/ref=sr_1_1?ie=UTF8&qid=1340914795&sr=8-1&keywords=power probe 2 (best electrical tool ever made) Digital volt/ohm meter, good crimping pliers and strippers (not the kind that wears cheap perfume, either), Weather Pack insertion and extraction tools. Inspection mirror, flashlights, telescoping magnet, mechanical fingers, nut drivers in SAE and metric.
So guys what am I missing on the list?