My neighbor gave me an FM2n that was sitting in his garage. It's in pretty decent shape but there's a problem with the meter. (I put in new batteries, so that's not an issue.)
First, the meter reads way way way under, like an LV 6 stops under. And it takes a large change in light to make it change, for instance get it to read as a good exposure (by setting ISO to 6400, etc.) on a bright seen then I have to almost cover the lens completely to get it to read under as underexposed. And it's very hard to get it to read for correct exposure, it jumps from overexposed to underexposed reading and requires careful adjustment of the scene brightness to get the "o" to light up.
Changes to the controls, shutter speed, aperture or ISO effect the readout immediately and have the normal responsiveness.
My (uneducated) guess is that something like a piece of foam has lodged right in front of the light meter, where ever that is.
It sounds like something got knocked out of alignment. The other issue sounds like a dirty ring resistor or broken ring resistor. Is there any impact damage either to the prism area or around the shutter speed dial? The FM2n's ring resistor is below the shutter speed dial.
The body looks well cared for, no dings at all, just that long-time-unused patina haze. I've discovered this problem is intermittent, while I was playing around with it for a while it started giving realistic readings. Then this morning I got out the F4 (my reference ) to compare it and it was back to extreme overexposed readings.
Maybe when it gets warmed up again the meter will start working correctly again.
For metered usage, it's a toss-up between the FM2n and the F2AS. Both have the same meter readout, which is easy to read in low light, unlike the needle systems of the Nikkormats and F finders (as well as the F2 Photomic and F2A, plus the FE series), and provides more information than the F3 and FA meters.
If I don't have to rely on a meter, then it's the F, awkward shutter release positioning and all. That camera, however, is about to be equipped with one of the old school selenium clip-on meters that slide onto the nameplate. Won one on evilBay.
For non-F2 cameras, I use either Northwest Camera Repair or Camera Clinic. Both are in the Seattle area, and both do a good job. An overhaul runs $138-$148 through both shops. That includes refoaming.
It's possible that Pete's kid, Alexis (Alexisdfl on eBay) might do it. Apparently, said person was a technician for Pete. There's also Judy B (don't remember how her last name is spelled, but she runs the marmot5767 eBay store) in Maryland, who a few Nikonians have sent their gear to.