Great find if it works! I would say it needs new light seals at least. Do you have a battery to test the meter? Not that you have to use the camera's meter, but it's nice. I don't put zooms on my SRT's so I'd go with the Vivitar 50, but that's just me.
I used alcohol or lens cleaner to clean the mirror. There may be other options.
I ordered some batteries to test it! I think I’ll receive them tomorrow. Also, need to buy some foam to replace the light seals. I watch some videos about how to do it. Hope I’m able to do it

About the lens, I thought that the 20-70mm has more versatility? But as I haven’t used any lenses before I’m a bit lost. I watched some videos about it to understand better how they work, but I won’t know what I’ll prefer until I try some. I thought about going with the Tamron because the other camera I bought come with a 50mm lens. So this way I’ll be able to try both kinds of lenses. But we still don’t know if the Fujica works and the lense is not compatible with the Minolta without an adapter!