You are correct, most and usually all maintenance can easily be performed by the owner. In fact, the owner's manual covers basic maintenance.
The owner can even rewire the s.m., following a good tutorial, with some basic skills and attention to detail. There are many sources here and on the web.
I have successfully rewired Singer lights, replaced wires to foot controllers, and rewired my 15-91. DH did the soldering for me, as that is a skill I haven't learned yet. The correct tools are necessary, and relatively inexpensive.
You can even dissassemble, clean, and reassemble the cam stack on the 401. Find some good resources, go slow, take photos of.every.single.step. (My 401 needs a spa day.)
Enjoy!