I am familiar with the descendants of this camera, and they have always been one of my favorites - not least of which for their oddity.
The camera you have begat the Ricoh 500, which is documented pretty well on Karen Nakamura's excellent website:
http://www.photoethnography.com/ClassicCameras/Ricoh500.html
I have a 500, and am not satisfied with the quality of the images - to me, the lens is not sharp enough and lacks contrast - I believe Karen felt the same way.
However, the 500 in turn begat the Five One Nine (spelled out like that, not "519" as one might expect), and that has a most excellent lens - nearly the last of the Ricoh bottom-winding cameras, and the best of them.
Interestingly, I have found several variants of the 500, all called 500 but looking distinctly different (frame shape slightly changed - smooth top vs stepped top - the 'step' being upwards of an inch!). I also have several models that supposedly do not exist - a 519M (they went back to numerics, huh!), which is a Five One Nine with a BEWI meter, and a 520, which is a plastic shadow of the Five One Nine, obviously the last of the line.
I love all of them for their shape and individuality - they broke the rules, eh? The 500 I have, despite having a disappointing lens (actually not bad for the era, just bad compared to the very sharp and contrasty Five One Nine) has the best viewfinder and one of the best rangefinder patches of ANY of my classic fixed-lens rangefinders. Sadly, much better than my Five One Nines, which have the superior lens, dang it.
I enjoy the 'wings' on the lens barrel that allow for focusing with either hand, very convenient.
The Ricoh 500G is a black compact fixed-lense rangefinder and is not of this line, although it is a classic in its own right.
In answer to your question - if it were mine, I would not invest much in repairing it, as the lens was not reputed to be all that. However, this is a camera that I might very well attempt to repair on my own. I have replaced a top plate on one of my Five One Nines by myself, and it seems to be pretty easy to work on. The rewind knob on top unscrews - stick something in the arms that hold the film cartridge below and then turn - comes right off - and there is no rewind lever to remove, so three or four screws and you've got it off. By the way, you're right that you have to hold the rewind while you crank the lever. And beware, it is fairly easy to turn both bottom knobs and open the bottom while the film's still in there. The 'two knobs' thing is more often seen in old folding MF cameras, seldom in 35's.
I hope you find this reply useful! I think it is a great and interesting series by Ricoh, sadly neglected as a collectible item, and very innovative!
Best Regards,
Bill Mattocks
PS - for a CLA, I do not have personal knowledge, but you might contact Mark Hama in Atlanta. This is kind of his sort of stuff. He's primarily a Yashica guy, but I believe he works on these.