[John Wood]

I'm sure on this engine you'll have to take the front apart to get the timing belt off and the cam sprockets off. That in itself is fairly major. Also you'll have to remove the exhaust crossover and rear exhaust pipe (converter) from the manifold. Otherwise it is a lot of disassembly and reassembly.
I did it on my 3.0 minivan and took care of a lot things including new valve guide seals and cam seals along with a new timing belt/tensioner and waterpump. I would suggest, as a minimum, picking up a Haynes or Chilton manual. It will really help give you an idea of what is involved.

Here is one picture I had with the heads off:

 

[valiant67]

This will be a very time intensive job. John is right on the money - fix as much as you can while it is apart. Water pump, timing belt, valve seals, etc.

 

[Oklahoma Wolf]

I've done this. Huge job. As mentioned, now would be the time to fix anything needing fixing... it took me and a friend a couple days to do this the first (and last for me) time. I bought a 1988 New Yorker for cheap with a blown head gasket and we put it back on the road again. Gasket blew due to a cooling system problem... turns out the radiator had nearly all its fins corroded away.

I ended up fabricating a cam sprocket holding tool from a length of pipe and some bolts, otherwise the only other special tool needed was a 10mm Allen socket for the head bolts. Speaking of which, I'd buy new head bolts to go with your new gasket set.

Definitely invest in a Haynes manual for this one. It's too big of a job to guess at it.