94 Vic - Engine options/questions?

Ok guys, I have a 94 vic with approx. 150K miles, dual exhaust. Currently, comparing to a newer vic in better condition, I don't think mine makes much horsepower (probably a bit less than it did stock), the transmission is steadily failing, not to mention it needs a new paintjob (badly!). I'm really attached to this car, though, and have always had plans of doing a complete restoration when I had the necessary fundage. Still don't know when that's gonna happen, but I wanted to pick your brains about what my options are (within reason).

I want to make approximately 300-350 HP... can this be done easily with the first gen 4.6 engine? I have read I would need to use performance improved cylinder heads... what about an intake? I take it all this stuff would require computer modifications to operate properly?

Secondly, I imagine if I replace the cylinder heads, there would be no more burning of oil. Does anyone know what causes the valve stem seals to go bad on these cars? I heard it could be the EGR channels getting clogged, but that's a PITA job to keep those passages clean often. Could I replace the EGR with a newer model? I suppose that would require a completely new throttle body/intake system anyway... :(

OR would it be easier just to swap the entire engine out with a post-95 4.6?