This is an awkward one. If you were clever enough to replace or repair the lens assembly you wouldn't be writing here so all I can advise is to have a very close look at the lens and see if you can notice any slight variation in it's positioning. If you can see part of the lens is pushed slightly to the left then with a very fine blade lever the lens from the left to the right and at the same time switching on. It's often easier to get someone else to do the switching on and off for you. Make sure the batteries are fully charged too.
If you can get the lens to come out a little way then keep trying and it's possible it will realign and start working.
Of course it's possible you've fractured a nylon gear or two so that will be a specialist job.
All I can tell you is that if you can't get the thing to work yourself it's going to be very expensive. Maybe another check on Ebay for a transplant possibility.