Honestly... the cynic in me thinks this is just someone who has managed to steal "aquire" a wallet.dat from somewhere that has "several" BTC showing in it, but they obviously lack the password and sufficient hardware to attempt to crack it and they're just attempting to get someone else to do the heavy lifting to bruteforce the password...

Unless the "reward" is placed into escrow, I'd be inclined to stay well away from this.

Otherwise, go talk to Dave @ https://walletrecoveryservices.com/  He has a proven track record of helping to recover passwords.