If your doing timing belt your going to want a good torque wrench for the crankshaft pulley. Don't forget the all important piece of pipe that can slide over your wrench/breaker bar so you can break stuff free that is not being reasonable. You will probably also need Metric Alan wrenches/or sockets if your changing trans/diff oil. PB Blaster is nice for those rusty nuts. A ODB2 reader can be invaluable to have around on a high mileage truck so you can check it and not have to worry about it being serious or just smog crap. When you buy sockets 6 sided sockets would be preferable to 12 sided under most situations because the 6 sided socket will "grip" more and less chance of rounding off.

2nd the jack stands. Jacks are for lifting the vehicle. Jack stands are for supporting the vehicle. Don't get under the vehicle without it being on jack stands or at least a tire that it can fall on instead of you!