This perspective correction was done all the time. It's very effective.
It can throw off the focus of the image on the easel. Stopping down can help with the focus if the "correction" isn't too severe.
What to do?
Small corrections in the negative holder can be used to tilt it in much the same way as a view camera uses shifts and tilts of the lens ...
Most of it is common sense. I am a maniac, so let me categorize things. Maintenance, in general, is divided into two categories.
The first part is to actually know the stuff. So take a screwdriver, on a clean desk and try to disassemble some ...
Here's what I'd do:
Take it apart and blow it out with dry compressed air
use specific bulb designed for enlarging if you change bulbs
clean the condensor (s) with lintless wipes and use lens cleaner
spray some wd-40 on a rag and wipe the gears and tracks with it, use very lightly and sparingly
If the elevation lock is broken fix/replace it... duhhh!