Here is a site where you can get all the info:
http://www.nflarchives.com/
I think there is a limit of 125 players, so you will have to make some decisions. What I did was to create separate files for each decade, and I only named the key players and players that I remembered for each team. So yeah, it sucks not to have the whole team, but it is better than nothing. Also, since they are separate files, I can't play a team from the 50's against a team from the 90's (Which is OK with me since I don't get into cross-era contests.)
The 125 player limit will hopefully be done away with next year. It will also be nice to be able to use historic teams in a tournament. A few retro stadiums would be nice to, as using the old time Vikes, Rams and Colts in a dome just kills the atmosphere for me.