Internal coolant leak(s)

I have a 2000 Mazda Protoge ES with the following details:

DOHC 16-valve
1.8 L I4 w/SMFI

79,000 miles

The car has been running fine. In the last week I found a CEL code for random misfire and misfire in #4 cyl. I removed the plugs thinking that the ignition system may need replacing. I found coolant in two cylinders which tells me that the head gasket is leaking.

I'm looking for advise on doing the job myself (e.g., parts, special tools, known problems, etc).

I am not a pro but have extensive experience under the "shade tree". Even built/rebuilt a few engines.

Thanks!