Door locks & Wiper question

[Amuso]

Can the door locks be replaced easily if I manage to get a new set of tumblers etc from another car? I am guessing getting a new spare key is not cheap, and it does not fit the rear trunk door anyways. Is it a hard job to replace all the tumblers/locks on the W124?

Also my wiper seems to "struggle" a bit when the windscreen isn't wet enough. It works slowly. Anything to adjust, rebuild, or do I need a new wiper motor ?

Work starts sunday on working my way through the car and see what needs to be done and check the electrical system as some things work occacionaly. Also a lot of electrical left over stuff from the ambulance setup which is more or less useless now.