Big question! I’m not a Resolve editor, but this is not specifically a Resolve issue. First, get perspective. Go back to the earliest, highest-quality digitization. That would be the original MXF. Open those files directly, in both an NLE and in VLC. They should look essentially the same. And also quite small on your screen at actual size. Remember, this is interlaced standard definition. You probably haven’t seen this in a while and it’s awful compared to modern standards. You do this because you want to know exactly what things looked like before anything mucked them up. It will look low res and lack contrast and color compared to modern footage and that’s just what it looked like. As I said, perspective.
No LUTS. Make sure your timeline is Rec709 because that’s what your footage is (actually it’s pre 709 but essentially the same). It wasn’t shot with a LUT. Just color correct. Depending on how your scopes are setup, your blacks may seem high. Standard definition was not shot full range.
I’m sorry I can’t help you with replacing in Resolve. Premiere has a “Replace” function which allows you to swap in a new clip while retaining all effects. I would hope Resolve has such a function.
Deinterlacing. This is the critical resolution step. Premiere is lousy at deinterlacing. Resolve, I don’t know. I would deinterlace and scale the original, probably with something like Topaz AI, but it is tedious and time-consuming and maybe unrealistic for a full show. The alternative would be to edit and master as interlaced standard definition and then deinterlace and uprez the rendered master.
Just a few tips. I’m working on an old show that’s gone through multiple iterations and it’s just a mess to decode what’s been done to it. It takes a lot of patience, shot by shot.