Sunroof seal

[86porsche]

hey again. another question I need an answer to? My sunroof has had a leak since I got it, but this has become much worse in the last few weeks. The p.o had bought a new seal but never fitted it. so I have the seal (2) small and big.

My question is has anyone fitted one of these?
Is there much too it?
anyone with pics procedures etc?

I cant find it on the manual and want to get as much info as I can to save time. I have checked the drains and all four are free. I just poured water down each one this evening and all was OK. I only seem to get the leak when I'm washing the car! do others have this problem?