Its a worn ratchet mechanism that you cant buy without replacing the whole lever body complete.
Ive had it on my 10 speed for years and I found that a slight amount of pressure on the upshift lever as you downshift stops the overshifting downwards. By applying a little pressure on the upshift...
If its a few little chips Id go to boots with a colour sample on your phone snd see if you can get a nail varnish match. Otherwise get some model humbrol paint and mix it until you get a decent match.
Put a wanted add on here for the wheel or rim and hun if you fancy building a wheel. Otherwise ebay will throw one up now and then. Gil at retrodecals will sort new decals if you need them.
Ride it once its done and see how it feels. I actually prefer the ride of my marin to the 93 Kona Explosif that i had. Id say it’s probably a keeper but depends how it feels when you ride it really.
Well done on getting it. I looked at this but it was a bit far away. I love mine although it’s a 1992 not a 94.
Strip it down, Clean it up and enjoy it. They really are nice to ride and rapid if you’re that way inclined.