Electical problems 2

I have an 1984 GMC S 15 Pick em up truck. I had it running great till the other night. I drove to my friends, truck ran great, had the radio on the heat was on. got there and parked no problems... when I was leaving I put the key in and turned it and nothing lol,, I turned on the headlights they were very strong! but no power anywere else... now a few days ago I put a CB radio in and wired it srait to the battery but made sure it was turned off when the truck was'nt running. also the heat fan would make a bad noise when it was turned on but it stoped after a few minutes.. Im not a machanic but when it comes to anything electical I can get the job done most times lol...
can anyone lead me in the right direction