I know plenty locksmiths because when I have more than enough work I have to find one to cover me. They would all say the same thing ... don't put WD40 anywhere near a lock ... and if you do use it, make sure you remove it afterwards (as in wipe it clean) and use a suitable lubricant.
Either graphite, grease, vaseline or a silicone lubricant, not WD40.
Old desk locks can usually be taken apart and cleaned and greased before being assembled, that's providing they aren't riveted together. They tend not to be too intricate and you will probably find rusted springs and a bone dry back plate in them. If you do intend on having a go at it take a picture of the lock when you initially open the case. This will help with re-assembly.
As for a website about locks the guys at
http://www.ukbumpkeys.com/
have all the answers about every kind of lock available. If you watch the multitude of videos available, it will get you thinking about your own security when you realise that almost all locks are fairly easily opened, especially your front door. I've been a member on their site for about 10 years and they are a very friendly bunch and cant resist helping solve a problem !