As others have pointed out, measure first. Might not be neccesary - on gasoline the seats don't wear much. Main use we have here (Netherlands) for valve adjustment is for propane dual fuel cars (like mine) which eat a set of exhaust valve seats in about 100K and need adjustment every 20-30K.

Most important is a set of feeler gauges, preferably offset (or bend the tip of straight ones a bit). As for the special tools, I have a shim depressor (Midlock brand) that I absolutely hate, a big flatblade screwdriver works at least as well for depressing the bucket, and a very small flatblade with the tip filed down a bit works great for flipping the shims out.

As far as cost, that depends. Couple of bucks per shim from Volvo, pricing from machine shops varies. I usually paid $1-$1.50/shim, this morning my favorite machine shop must have had a particularly strong case of good christmas cheer and sold me 10 shims for $5.

You could also go down to the pick'n'pull, practice on their heads first and grab a couple dozen shims from them - can't be very expensive I think, or even free depending on your morals. Shims don't typically wear.

Oh, one important tool: digital caliper cauge or micrometer - the markings will be nonexistant or rubbed off, so you need something to measure down to 0.05 mm, preferably 0.01 mm, to know what thickness shims you have (needed to calculate the needed ones) and to check the ones you got ("Now was this the 3.7 or the 3.75 that I just bought?").

Bram