While your tutorial is wonderful, it work only on unencrypted wallets from what I see.
If the wallet is password protected, the signature seems to change to 08 02 1A 21
The following bytes seem to need some more operations to become the correct private key.
Yes it only works on unencrypted wallets. There's a tool called wallettool in bitcoinj that can decrypt .wallet files and extract private keys from them. However, it requires installing and configuring a load of software, and using some quite technical command line instructions. Furthermore, if a .wallet file is slightly corrupted wallettool might not be able to work on it
The whole wallet file can't be encrypted because there's some human readable text at the start of an encrypted one. If only the unencrypted part was corrupt, it might still be possible to work on the encrypted part using openssl. Multibit encrypts .key files using openssl, and it probably uses openssl to encrypt .wallet files too. There's probably a way to decrypt them using the openssl command line. There's a tutorial explaining how to decrypt a .key file using openssl here.
https://multibit.org/help/v0.5/help_lostOrForgottenPassword.htmlUnfortunately I haven't yet found a tutorial explaining how to decrypt a .wallet file using openssl, or figured out how to do it myself.
Nevertheless, the OP said his wallet file wasn't encrypted, so that shouldn't be a problem for him.
i have only original .wall .info files and data file ,it was not encrypted , i had not exported keys at that moment.