Yessir. Oil in the coolant tank is definitely a sure sign of a bad head gasket. I would advise doing it sooner rather than later. All of that oil circulating through your coolant system is really gumming things up.
It's not a
hard job. There are just a lot of steps, or "mini-projects" as I like to call them. There aren't too many special tools needed. It should take you a long weekend to complete the job.
You will need to decide how thorough of a project you want this to be. At a bare minimum you will need to replace the head gasket itself, and buy new bolts.
But there are a number of maintenance items that should be done IMO (and are easier now, than later), if they haven't been done already. Including but not limited to:
-Belt tensioner
-Water pump
-Chain tensioner
-Check plastic timing rails
-Valve stem seals / Valve guides (if needed)
-Buy all new cylinder head sensors (approx 3)
-Buy all new rubber coolant hoses (including the short one in between head/WP)
Here are a few threads that might help:
300E Heads R & R What Else?
M103 head r&r more pics, what's with #6 cyl?
Head Gasket help on a 190 E 2.6
Replacing a head gasket on a 91 300E