They're lying to you. They cannot retrieve the wallet passphrase from a wallet.dat using a hex editor.

The only solution is to attempt to bruteforce it. You can use something like btcrecover or hashcat or "John The Ripper"... but they are not exactly "newbie" friendly. They require a bit of technical skill and are all commandline programs.

Another option is a "trusted" password cracking service like Wallet Recovery Services... The owner (Dave) has been on these forums for a while and has a number of successful attempts at password recovery for numerous users. They also have a thread here on BitcoinTalk: https://bitcointalk.org/index.php?topic=240779.0