Milgard sliding door exterior key lock

Thank you very much for your time.



This looks like a handle set with 4-15/16" hole spacing--if so, see our keyed 82-081. I am afraid we can't provide locks that work with the same key. A locksmith may be able to assist you.

Can't find any installation instructions.



If your mortise is in good working condition then there shouldn't be any need to replace it, no. That is also of course assuming that the 82-081 is an identical match for your old handle set, which I can't really verify based on the provided information.
Your first step should be to make 100% sure that the 82-081 is the correct match. You do this by carefully comparing size and design; if they differ in any way, then there are good odds it's not the right match. I'd be happy to review it for you but I would need photos of the original handle set to get started.
Assuming that they are a match then your next step is to examine the condition of the mortise. You can use a slotted screwdriver to manually turn the hole that flips the hooks. If it works normally, then the mortise is fine. If it hangs up, then the mortise needs to be replaced.
We can help with that, too, but I would again require photos of the mortise in question.