| But you have to get your car to stop smoking before it gets lung cancer!
Seriously, valve cover gaskets are really easy for a backyard mechanic to handle. Head gaskets are similarly within the scope of your average wrench-spinner.
Cam valves or the crank seal (I assume you mean either the front or rear main seals?) - those are quite difficult, requiring the services of a competent mechanic.
A quick test - steam-clean your engine, run it for a few minutes and see what's leaking from where. You can then decide whether to put an afternoon of elbow-grease into it, or get a real mechanic to fix it. | 
