It is a 1999 BMW F650. The transmission was slipping out of 2nd gear. This is the process of replacing the gears.
Step 1. Remove the engine. Use the instructions from http://faq.f650.com/main.html
This is the document I wrote about Splitting the engine case_(pdf) Download this document for detailed descriptions of my process for splitting the cases
Buy a new head gasket.
Spend some good time learning how it works before tearing it all apart. It will help when it comes time to put it all back together.