Ok, is the problem the battery if:
I go out in the morning and start it, but it cranks slow and won't fire then crapps out, interior lights work and whatnot, guage reads in the red (8-9), I get a jump and fires right up, drive around with lights, stereo, wipers and heater on for about 1/2 hour, guage reads a steady 15 volts. Come back, turn off all accessories, turn off truck, immediately afterwards, turn the key back to "on" guage reads 13 volts, turn to start.....cranks slow and won't fire, let key off start, guage reads 8-9 again. Is my battery shot??