I am having bad mileage issues and I think that I should start with replacing the spark plugs. My questions are what brand should I use and do I need any tools other than a socket wrench?

I personally only use ngk plugs. i've been using them in my 99 and now in my 04 for years now and they last a lot longer than the champions and bosch plug (jeeps hate bosch anything including plugs) other than a plug socket you'll need a 13 or 14mm socket as well for the coil pack if it's an I6 i don't know how the v8's but the I6 it's a couple of bolts a wire harness at the back and the plugs themselves. takes 20 min. Grease the boots with silicone and get some anti seize for the plug threads

I agree with everything hulkmn069 says, except i like champions in mopars, a.c. in gm, motorcraft in ford, ngk in asian imports, and bosch in european imports, so i'd use champions

Thanks all for your replys. I am going to try it this Saturday.