I'm parting out lots of things from my car. If the model year 2000 and 1998 part that you need is the same, I have it. The convertible top motor itself is about as easy to change as a tire or two (three mounting nuts, one electrical connector, two snap-in cables). I know because I removed it and everything else related to the convertible top from the car last week!
Parts list here:
http://www.bombaydigital.com/boxster/parts/boxster-parts.pdf