You will need an appropriate wrench set (the head bolts are sometimes hex head, sometimes not), a torque wrench (preferably a "clicker" type), a strong back and a helper. You will not be able to lift the 5 cylinder head off by yourself unless you are pretty husky.
I'm not sure I'd tackle a head gasket replacement as my first "wrench" project unless you have an eperienced buddy to help you -- it's fairly easy to damage the head if you don't understand the instructions!
Basically you remove the valve cover and anything attached to it, the intake and exhaust manifolds, any interconnections between the head and block like water tubes, thermostat housing, etc; injector pipes (you can leave in injectors in the head for just a gasket change). You also need to set the engine at exactly TDC on #1, so that you can CAREFULLY remove the cam gear and tie it up to hole the chain in place.
You then take out the head bolts and pull off the head, manuvering it around the chain -- the chain has to stay pulled up tight so it won't jump a tooth on the injection timer or crank.
Once the head is off, you clean it and the block, put a new gasket on, put it back on, torque the headbolts properly, re-install everything you took off, and you're done.
For a first time job, plan on a weekend. More if you do something like drop the chain, as you will probably have to re-time the injection pump, pull the chain rails, etc if you do......!
Gasket set for a 603 is about $165. Cheap compared to the time to get the head off and back on.
And do check the head while you have it off -- if the head gasket is blown on a 603 (the 6 cylinder), the head is usually cracked and will need to be replaced ------!
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!