Battery Light On

I have a 2001 Silverado, Ext Cab.  It has a 5.3 liter engine.   I got in it and started it up and immediately turned the AC on when it (the AC  just died ,fan and all) then battery light came on in the message center.   So the first thing I did is checked the battery terminals (ok) next went to one of the local parts houses and had the battery checked(ok), they checked the alternator which checked low, swapped out the alternator, the battery light is still on. The heat gauge, gas gauge, the odometer gauge do not come on now.  I checked the fuses in the fuse box on the left side of the dash kick panel and they checked out ok.  I then checked the fuses under the hood and they checked out ok.  Is there some inline fuse controlling the power going to all these accessories that I am not checking because I am checking them with an ohmmeter for an open circuit and they are all reading 0 resistance?  I don't know what else to do please help.
Thanks 

weird one, only thing I can thikn of that might be easy is a bad ground somewhere when you swapped the ALt.....

I think those trucks have had some problems with the gauge clusters.