You're welcome! I'm glad to know that this is still helping people years later.
If gears are popping out during a turn or acceleration it's usually a bad bearing giving a shaft too much play. If you're grinding while shifting into gear then the syncros may not be doing their job, but it doesn't necessarily mean they're bad. There needs to be a certain amount of friction between the syncros and the gear in order for them to work right. This can be caused by oil that is actually too slippery such as synthetic or possibly even SJ(common) motor oil. This is why the owners manual specifies SF/SG motor oil. It isn't quiet as slippery as SJ but still slippery enough for the bearings and other parts to work properly. If the transmission is still in the car you might try changing the oil for SG grade 10w30. You can usually find SF/SG labeled as being for older cars or for motorcycles. Or a lot of people have had very good luck with Penzoil Syncromesh usually available at autozone and other stores. If you already have the transmission out or the oil change doesn't work you'll have to check the syncros and gears. If the teeth on the syncros are sharp then it's the interface between the syncro and gear. When you take it apart you'll notice there is a part of the gear that the syncro slides over and it's probably pretty shiny. That's the spot that needs friction. Over the years it's possible to have sort of polished it through normal wear. My friend had the same problem I just rubbed some of the shiny off with some sandpaper and put the original syncro back(after a thorough cleaning of course). Everything worked fine after that.
Hopefully this will help give you an idea of what you're looking for.
As for the paint you pretty much guessed it. I cleaned it all with brake cleaner and a wire brush. Then plugged the holes and sprayed it with high temp engine enamel. I did it while they were apart and just laid them on a cardboard box while painting. You can paint while it's together, as long as you get a bunch of paint inside it should be fine.