You need to post some close detailed pictures of the banjo with the resonator off with a good close up of the rim and pot assembly. Not all of the 70s banjos were bad. You need to determine what exactly you have before you start changing things up that might not need changing at all. Nothing wrong with removing the neck and there are probably YouTube videos out there that you can view to tell you how to get that done. I would start off with some mild soap and water first to see exactly how clean you can get it with the pretty basic cleaning agents. If more is needed, go to one of the banjo merchandise suppliers on line and see what they have and go with that. (Banjo Ben, Bob Smakula, Elderly, Banjoteacher.com and others comes to mind.)  Same for any wood cleaning item if you want to work on that area as well. Just get the pictures up and there will be plenty of knowledgeable folks willing to help you out after they see what exactly it is that you have. I do see where you put three photos on your page but some of the neck and peghead would help as well.  Also if there is a serial number post that.  Should be on the back of the peghead if I remember correctly.  

Bobby

Thanks so much BobbyE, I initially posted with pictures but it failed so I'll try an put them here.

Serial number is 101617. 

More pix:

You might want to weigh the tone ring while you have it apart. Some of them were quite "light". Others considerably heavier.

Is the 5th fret inlay missing?

I used simichrome and an old t shirt to clean up my 1926 recently (see recent thread in here for pics). Came out great.

Not too many places left in NYC to buy banjo accessories. Guitar Center and Retrofret (in Carroll Gardens, Brooklyn) should have banjo heads. Guitar Center has only two different sets of banjo strings in the store. One of its NY stores had only one set.

You can get a head and D'Addario strings online from Smakula Fretted Instruments. Bob's a member here. Larger selections of strings are available at Elderly.com and StringsandBeyond.com.

The easiest big improvement in sound will be getting a new bridge. I, and many others, like Scorpion bridges. Made by Silvio Ferretti in Italy. But available here in the US from Banjo Ben's Warehouse, BannjoTeacher.com, and maybe also Elderly. Dotson bridges and the various models made by Kat Eyz are also popular and good sounding.

Tailpiece is next. I'm partial to the Kershner style. But I have a parts banjo with lots of 70s RB-250 parts and it sounds pretty good with the original Gibson clamshell tailpiece. I put some sticky-back velcro under the cover to keep it from rattling on the strings.

I second the suggestion of Simichrome polish for the metal. Use it once, you may never have to polish the parts again.

Definitely start mild with cleaners for the wood parts. Maybe use Gibson guitar polish -- the liquid in a pump bottle -- and a microfiber cloth.

If there's a musty smell in the banjo case, that's going to take a lot of work.  Start by sprinkling lots of baking soda in it then leaving it outside, open, in the sun. For several days. Vaccuum it out. Then consider spraying the inside with a dilute solution of white vinegar and wiping the interior to be sure it gets everywhere.  Then more baking soda to neutralize the vinegar, more sun, and more vaccuuming. Finally: I put some coffeemaker charcoal water filter packets in a musty case after doing all the above, and it's been odor free for a couple years now.  I keep them in the case with the banjo. One sits on the flange when the banjo is in the case. It used to have a smell and now it doesn't any more.

For that missing inlay, contact Tim Davis - https://www.davisbanjosandinlay.com - to find out if he has that specific piece in the exact size as used in the 1970s RB-250. Richie Dotson - https://acousticbox.com - is someone else to try. He's authentically duplicated most or all the pre-war Gibson inlay sets. While the 1970s Gibson inlay copies one of the pre-war designs, I don't know if the pieces are the exact same size. Richie might know.

Even if the piece is a drop-in fit, it's probably going to need sanding to bring it down flush with the fretboard, and that's tough to do with the adjacent frets in place. Maybe your banjo could use a fret job. Or at least a partial.