It really depends how soon you want to get rid of it and what area you live.
I assume you will be selling locally and that it works (as in good belt, brush roll adjusted)...
Having the original wheels, floor wands, floor buffer, handi butler + buffing wheels, hose, and basic attachment set is a big plus.
Leave it as is and start at 75. I would not take less than 50 though.
Now you could get some Mother's aluminum polish and do a metal polish and wet-rag treatment to the other parts. With no disassembly, this would take a few hours and you could start at 125 and take no less than 80.
Or you could go extreme like I do and tear it down, restore everything, replace bearings, wash and polish. This takes me about 24 hours, excluding attachments. Then you could start at 350 and see what happens. If you go this route, you might consider ebay and raise the price more. I have seen some nice ones sell for good money. Having them in like-new condition sells. Many people want them for nostalgia and do not want dirty vacs, and many (if not most) will not want to work on them.