There are a good number of shops in Cooperstown. I went up there for my little brothers baseball tournament last year. I don't remember exactly how many there were, but there seemed to be one on every block.
I didn't bring a bunch of money, so I just bought of couple of minor league base singles of a few Mets players.
To go through the whole Hall of Fame and really look at the details would take a few hours. I went through it in about an hour and a half, but I walked by most of the stuff after glancing at it.
I hope this helps. Enjoy your trip!