Sptt! read the advice again, don't use any oil on the gasket. If you could do that you wouldn't need the plastic piece!

Very specifically, all the surfaces where the gasket will lay must be thoroughly cleaned and the wiped down with a solvent to remove all traces of lubricants.
This is a DRY job with sealant used only in corners, top and bottom, of just the ends of the gasket.
The only lubricant I could recommend, would be some spit or a light swipe of water on top of the gasket to help the plastic slide out. The spit will quickly dry. Even this is only if needed, which is why I suggested a dry run to see what to expect. I didn't have to use anything when did them.

This is a notorious point of oil leakage on these motors and from all I've read, if they aren't done right (procedure and materials) they'll be leaking again soon. Well over a year on one of them and it's still dry.