changing un/lock sounds on ipad 1 - where to find them?

Great info Fid, but the OP said they didn't want to use Winterboard to apply themes

OP, if you want to do this "manually", you need to replace the files in

System/Library/Audio/UISounds/

The files are lock.caf and unlock.caf (these are a special format audio file which you will need to create)

But be WARNED! Modifying the stock system files is dangerous. Don't do it unless you know what you are doing! If you mess up your system you may have to restore and may lose your jailbreak.

Winterboard is a file substitution system and therefore very safe and stable. IMHO you should use it, even if only to substitute these 2 files and never apply anything else! Follow Fid's advice and create a theme

 

It's the themes you apply in Winterboard which have the potential to hog ram. It is simply a file substitution engine and actually very efficient. If all you use it for is to replace these two files with one simple theme the impact will be absolutely minimum, but it's your choice of course.

Sorry, I don't have any sources for lock sounds. Why not just download them from Cydia though. You can then use iFile or your SSH client of choice to retrieve them from the Themes section. You can then remove the packages from Cydia (and Winterboard if necessary) after you have the files saved away of course

 

No. Be sensible
All things use RAM, but Winterboard only uses a little RAM in the grand scheme of things. It is the large themes which folks apply with Winterboard, and replace ALL the graphics on IOS, which use a LOT of RAM. Substituting a couple of sound files to replace lock and unlock sounds will use a tiny amount of RAM.