1992 Porsche Other oil

I have 1992 Porsche Carrera 2 cabriole before put in storage there was black suet forming on bumper near tail pipe, it has been in storage for 3 years I put gas preserver in tank, started with jump last week, white smoke for a while then stopped thinking of changing oil, any reason not too, also air condition no cold air can I replace Freon myself can I fix this myself