If it won't pass emissions, only replace the part that is bad. As far as a tune up. In general they include spark plugs, ignition wires, distributor car and rotor, fuel filter, and an air filter if needed. An oil and filter change should be done every 3000 miles, but the oil pump should be fine unless you lost oil pressure. They rarely go bad. The same with the fuel pump. If it still works, let it alone. A fuel filter is good preventative maintenance, as is transmission service every 30K miles, and the radiator flush should be done too if it's over 3 years old.
Finally, the leak on the passanger side that smells sounds like the heater core is leaking. Yes, it needs fixed. As far as the a/c if it only blows on the windshield and the floor, there either is a vacuum leak (which directs the air flow) or a vent door is damaged.
Listen, you have a lot of questions. I tried my best, but if you have something specific, let me know. Also, follow the owner's manual maintenance schedule. It will provide what the manufacturer recommends.
Let me know if you have other questions.
Saturday, January 31st, 2009 AT 3:20 PM