GPX600 - replacement engine or reco?

Okey dokey, here we go.
I have an old GPX600 which has been great, the only problem thus far has been a bit of an oil drip which I have been putting off fixing. I went on a ride today and got stuck in a fair amount of rain. Lost the back tyre at one stage and got spooked so I pulled over, when I smelled coolant and saw a bit of steam coming up from the front. I headed off again to get to the next town in case it was a leak and was going to get hot on me...
It was fine on the way there and didn't miss a beat, no more coolant smells so I'm not sure what that was all about. After the stop for lunch, the bike started but was reluctant to keep running, and then under any more than light throttle was missing - but it would maintain a steady light throttle (ie. constant speed or gentle acceleration) without incident.
These symptoms kinda point towards a possible blown head gasket. I did some searching, and whaddya know... a number of reports on BHG's on Kawasaki GPX/GPX motors of this vintage.
As it's got an oil leak and this possibility, I'm thinking I might rip the motor out and rebuild it. Being a Kawasaki forum I was hoping you guys might have a bit of experience with these older bikes and could warn me off doing it if appropriate, or give me any advice.
Also an idea on things that should be looked at while it's apart would be great - and any idea on what a full rebuild kit goes for these days?
I have an old GPX600 which has been great, the only problem thus far has been a bit of an oil drip which I have been putting off fixing. I went on a ride today and got stuck in a fair amount of rain. Lost the back tyre at one stage and got spooked so I pulled over, when I smelled coolant and saw a bit of steam coming up from the front. I headed off again to get to the next town in case it was a leak and was going to get hot on me...
It was fine on the way there and didn't miss a beat, no more coolant smells so I'm not sure what that was all about. After the stop for lunch, the bike started but was reluctant to keep running, and then under any more than light throttle was missing - but it would maintain a steady light throttle (ie. constant speed or gentle acceleration) without incident.
These symptoms kinda point towards a possible blown head gasket. I did some searching, and whaddya know... a number of reports on BHG's on Kawasaki GPX/GPX motors of this vintage.
As it's got an oil leak and this possibility, I'm thinking I might rip the motor out and rebuild it. Being a Kawasaki forum I was hoping you guys might have a bit of experience with these older bikes and could warn me off doing it if appropriate, or give me any advice.
Also an idea on things that should be looked at while it's apart would be great - and any idea on what a full rebuild kit goes for these days?