Any good advice???

I have a 2001 Z71 and have had little problems out of it. I've taken it to the dealership twice to have them tell me that the TPS sensor and Fuel gauge sending unit are no good and that they are not covered under my warranty. I replaced the TPS sensor and havent worried about the fuel gauge since it works 95% of the time. It just drops to E when you fill it up. Now that my truck's warranty has just ran out and the SERVICE ENGINE SOON light has came on, I don't want to take it to the dealership to have them charge me $50 to hookup there machine. Where and what can you buy to do this yourself? I have checked out the autoxray.com website and they have a scanner for $80. Is it worth it? Any good advice???