As most have said, all fluids, front to back. "Cheap" and easy.
Clean the engine, this includes the underside and trans. Steam clean is preferable. Engine runs cooler, much nicer to wrench on and much easier to track down leaks as they occur.
Next, I would look at the stuff that will leave you stranded. Coolant hoses, fuel hoses, belts. If they haven't been changed, just do it. The hoses will, in some cases be hard as rock. Coolant hoses don't have a warning indicator, just replace them. Don't forget the PHH.
From there, I would replace the radiator. The transmission line runs through it, if that line corrodes, you have a pink milk shake in the trans and a major spendy repair. Cheap insurance. If the radiator is out, replace all power steering and trans lines in that area, trust me, you will thank me latter.