Andreas,
The sump gasket area is known leakage point and nothing to worry unduly about.
The stiff clutch doesn't sound too good together with late take up point but again it could just be due a fluid change or bleed.
There is a good buyers guide to your era of Plus 8
here at the rear of the book.
If you can't get a copy pm me and I'll scan the pages in and email to you if you wish.
Good luck with choosing your next playmate.
