Honestly, if you think you have it in you to re-seal it, then you should have no troubles. They are not very complicated. Talk nice to a dentist about some broken or no longer used dental picks, or keep an eye out for some at the tool stores, as they really rock for pulling small seals out of the grooves. Also handy for the one-way washer that holds the cartridge cap together. You hook under each of the end pieces in turn and you can walk it up and out. Easier than wrecking it to remove it.
I would suggest getting the seals you need there, then installing a CO2 cartridge in it and carefully listening to where the actual leak or leaks are, and simply replacing those seals right off. The usual suspects are going to be the small seal on the CO2 cap center, as well as the larger outer seal, and the main valve. A drop of pellgunoil (CTire) or ATF on your fingers while handling the seals will help some with having them sit and seat in well. A drop of same into the works of the valve (via the cartridge cavity in the grip) can sometimes be all it takes to seal up a main valve, too. Worth trying first.
Take care to not pinch or cut the seal on the main valve body, as you slide it back in past the screw holes. You'll be fine!
Hit Crosman's website a dig out the book of words and pictures. They have the stuff there for download. The exploded diagrams in the parts list are gold!
Last one I sold, netted me 125, sight unseen, from a fellow that used to deal in airguns in the Edmonton area. That was a rather profitable trip to the gun show, as I bought 4 air pistols for $100, with the grocery money. I would have kept the Mk1 but I needed the groceries too, and knew I could flip it the same day. One of the other guns I got was an absolutely MINT Hammerli Single in the box with papers etc., that I sold to a collector in the States for rather a lot more!
I would suggest that in that region would still be a pretty good ball park for value. They are great shooters, feel good in hand, and are accurate. You should check out the customs that Tim at Mac1 Airguns does too. Dunno if he's still offering $100US each for donor guns for them, but it shows some of the potential for customization.
Most, but not all of the parts can be still got. IIRC the tube for the hammer that was cut for the power adjuster, was no longer available from Crosman, and I did a small run of them for the airgun shop at that time. Easy to make with hand tools, from some 4140 tubing of the correct size. But yours should be good.
Cheers
Trev
