If the chain isn't stretched, leave it be. If you prep the new head before you pull the old one, you should be able to swap the head and get it back on the engine in a weekend if you're working by yourself and unfamiliar with the job. If you've done head work before, or if you have a helper, you can do the job in a day. I was terrified to do this job on my SDL since I'd never pulled a head before. After the job was done, I didn't see what all the moaning was about, it wasn't that bad.

Take the time to prepare what you need before you start. Have all the gaskets, nuts, studs, etc in hand before you start. Print off or obtain the sections of the service manual for cam removal, head removal, and any other related parts. It'll make the job go a LOT easier to have it already in hand.

If the radiator is blowing coolant out of the top tank, it's time for a radiator. Pressurizing the system should pop the radiator cap long before it blows coolant out of a radiator seal.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]