I've done a few of these lately. They're a pain.

Parts wise, you'll need the rubber gasket that goes between the housing and the engine block, the one between the heat exchanger and the housing, and it's also worth doing the two PCV breather hoses as well, as you can't do one of them without taking the manifold off anyway.

Also, there's a fair chance you'll break the dipstick tube getting the manifold off, so factor one of those in as well.

The dearest parts were the two PCV hoses, at around $160 for the pair. Dipstick tube price will vary depending where you get it from, but probably around $20, and the two gaskets are about $45 the pair, off the top of my head.

There's a high chance of oil/coolant cross-contamination, too. So definately dump the coolant.