Need help with 1936 and 1939 Goudey Premiums

[Hordfest]

Good morning, I have some questions but first off, a little background. My late grandpa was an avid collector of all sorts of sports memorabilia. Before he died he gave a lot of it out. He gave my brother and I a bunch of stuff in varying conditions. One of the things he gave us was two very old envelopes that mom kept hidden from us until we were adults. It turns out, each of those envelopes had near complete 1936 and 1939 Goudey Premium sets in them, unsleeved and untouched for decades.

It is pretty overwhelming to go through these so I was hoping that some people were would have have some knowledge on these older cards beyond the very basics I can find elsewhere.

They are very neat, and have a close personal story to me but I'm really not sure about a lot of things like:

1.) Should I grade them? How do you decide which ones to grade and not to grade? SGC vs. PSA? I do want to sell some but probably not all of them?

2.) What is the best way to preserve them?

3.) Does anybody just have advice or info on these sets or on vintage baseball cards period that would be helpful?

Please share your wisdom with me! I want to make sure I do things the right way. I have photo soft sleeves and top loaders on the way as a first step.