Best/Proper Way to re-bed keel?

I've going to have the keel off my Catalina 30 in a week or so. After inspecting (hopefully not replacing) the keel bolts, what is the preferred method of re-bedding the keel?

Do I try to seal the bolts for the full length of the threads in the bilge stub?

Is it okay to paint the exposed threads and nuts after it is back together or should I leave the metal bare? (Mild steel)

Should I even consider leaving the mild steel bolts in the keel?

If I should change them to stainless, how the heck do I get the old bolts out?

I only want to do this once!

I'm asking here, since the three shops that do this kind of work have given three different answers. If I decide to hire it done, I want to use the shop that does it right.

Thanks in advance!

Randy