I have a head gasket leaking antifreeze into #3 cyl. With 135,000 miles what should I expect to do while replacing the gaskets? I have plenty of domestic engine repair experience, first time into my Benz except for water pump and thermostat.

Open for suggestions as a DIY project..

At this mileage, I'd have a serious look at the timing chain.
Since you have to remove the head, a good look at the valves would also be wise. While you're there, valve seals (cheap) would be easily replaced.Good Luck
jackD

First:
go over your records.
any headwork done?
timing chain been replaced before?
then:
assuming these things have not been done before,
pull both heads,and have them checked for "flatness"
replace valve seals,check springs etc etc (whatever the machine shop suggests,providing they are GOOD!)
or buy already rebuilt heads.
also replace timing chain and "Rails"
inspect cam and lifters for wear,and replace if needed.
REPLACE the plastic oiler pieces that oil the cam!
(do this anyway!)
you will need a head gasket kit
(one for each side)
"Partshop" on this site is a good place to get these parts!
I think thats the majority of what SHOULD be done.
doing this while you are in there saves lots of Labor $$ in the future.

__________________
'60 190b
'77 300D
'78 240D
'82 300TD

You'll need a few of special tools. All but the head bolt offset hex bit you can make from items in your toolbox.

Sixto
91 300SE
81 300SD

I appreciate the good advice and quick response. This is a great site for MB owners. Thank Ya'll