Yes, you will need to go in from below.
Deoxit is not something I would recommend. Like WD40 and other 3-1 products, it's probably very good for something but
not a thing I would like inside any B&O. Contact cleaner is good for cleaning contacts but only if you can clean it all off afterwards.
Contact cleaner does not remove anything, it will only shift the dirt around and in the best cases it won't add to the mess.
You need to clean off the remains of the hardened lubricants and add fresh.
Acid-free oil will do fine, sewing-machine oil or so. Not motor oil or "everyman oil", it will evaporate too quickly.
Whether you can do the service yourself is for you to decide.
The service manual is online and download'able for silver & gold members though it does not provide much info regarding actual service.
Martin