........Start by removing the bobbin and bobbin case.
........The old grease is most likely hard.
.........Open the upper and lower areas and clean up all of the grease. Real hard debrees can be removed with carburetor cleaner.
........While turning the hand wheel you can spray this on parts to loosen the grease. Use qtips to remove the debrees.
........Use qtips that have been sprayed with carburetor cleaner to clean the plastic where the dried grease and filth is at. Try not to use carburetor cleaner on the plastic as much as possible.
........When the cleaning is finished use sewing machine oil on all parts that are steel against steel movement. (Not plastic or rubber).
........ For plastic against plastic use lithium or 100 % synthetic oil. These can be used in place of the grease because they don't become hardened due to wear and time.

I have resurrected several old (but good--Bernina!) machines that have been idle for a long time and the oil has dried. Even if your machine is running fine, it should be thoroughly oiled periodically to keep it humming.

Wheel on right side that controls the needle up and down is very tight...