I'll second changing all the fluids, which is oil, but also trans, diff, coolant, PS fluid, brake fluid, and oil your suspension. Did you change the fuel/air filter? Clean your air filter when dirty, replace every 15k mi (they're cheap anyways). Replace your fuel filter every ~30k mi (I personally think you can go a bit longer because new fuel tanks won't rust as much). Deal with rust before it becomes a bigger problem, especially frame rust.