I got my doors dipped by a place near Croke Park a few years ago, great job altogether. I manually stripped the frames, stairs etc. It will take you a long, long time to do this. The results are great but it is not worth the hassle - I wouldn't do it again. 70 odd years of white gloss - gives me a fright just thinking about how much time I spent scraping, sanding etc...
A friend of mine got his door frames and skirtings done by an expert decorator to look like wood, they are unreal - looks very, very good you've need to get very close and touch to realise, its "fake". I would investigate this route if stripping was not an option or just rip out as Leo suggests.