M103 Head Gasket Questions

It looks like I need to replace the head gasket on my '91 300E. The coolant has an oily feel and there is a oil blown back over the transmission that appears to be leaking from the head at the rear.

This car only has 54K on it and has had annual coolant changes using 50/50 MB cookant and distilled water. I can't believe that I've got this problem.

I'm going to take it to a respected MB dealership but wondered what I should insure they do:

- Cooling system flush w/MB cleaner?
- New timing chain cover gasket?
- Chain guide?
- Tensioner rail?
- Other?

TIA,
Bud