Just my 2 cents. I had to replace an oil pump on a friends truck. NOT fun at all. The "special tool" you will need goes around the timing chain and is supposed to lock the chains together and keep them from moving. The cams have a little notch in them that the chain sprocket rides on. You will probably need a pair of pliers to help get them back in place and HOPE the timing chain tool doesnt slip off. Dont want to jump timing. But back to the subject. Sounds like a head gasket. The sooner you replace it, the better. You dont want to be rebuilding a complete engine.
Overhead cams can be a PITA, but I have come up with a few tricks when working on them: First of all, I have yet to find a OHC gear lock tool that fits and actually works well, so I decided I will just use zip ties for the rest of the jobs I do(did so on the last one and went beautifully). I used the medium sized zip ties to anchor the cam gears in place, just looped them through the gears and anchored them to whatever I could. It doesn't hold it perfectly but close enough. Also, use a white out pen or white out or something similar to mark the chain and gear at a specific tooth at each gear, so if it does slip you can put it back to the same spot....things like this reallllly help save time and work...