I would want to take it down to bare metal. Without doing that, how will you know what's there? You wouldn't want to put the expense of a paint job on it only to have it start bubbling up in a year or two. Also, your new paint may not be compatable with what's under it. Last, I think three paint jobs would have it too thick.
Got a trade or technical school near you? You might check them out to see if they have an auto collision repair course. You might could take a few classes and do the work yourself.
C
