They're a bu55er to take apart and service, especially the trigger mechanism which uses a ball bearing mechanism and needs about three pairs of hands to put back together again.
Other than that, there are a few of them about, so they are not particularly valuable. With regards to power, don't expect much more than about 9ft/lbs.
Overall, enjoy it for what it is. I use mine for plinking in the back garden when I fancy shooting something a bit different.