It can be many things so with our more information it is hard to say. If it has gas then it more than likely does not have spark.
the alternator is bad
The starter could be bad. Or the battery. The starter could be bad. Or the battery.
the starter or the battery could of gone bad.
Are you positive the battery is dead? Have you tried to jump start it? That clicking could be the starter relay.
The starter or battery could be weak. The weakness will cause the starter to turn too slowly to start the truck.
Maybe Its Your Battery
Very likely an alternator problem; if the alt is not working soon the battery would be drained and the truck would shut off.
Yes why not, you can recharge your truck PC by driving around. To recharge the PC first the truck battery should be charged. Driving recharges truck battery because every truck has a power generator inside it but you cannot recharge your truck battery if it is not working properly the acid level of the battery should be maintained properly. Better you check your battery before recharging battery.
No, most plugs are for block heaters only.
could be a lot of things. I'd start with a battery tester, then starter, then go into the more expensive fixes.
Loose cables, bad battery, alternator or starter.
It could be the starter in it. It may be weak or need replaced.