Silverado Won't Start

I have a 94 silverado extended cab that won't start. About 2 months ago it seemed to start slow, sluggish. Once it started it was fine. Then everything was fine for awhile. Here, last week it started to have difficulty turning over. Last night it didn't. Now it just clicks. I tried to jump start it but I have some bad cables so it probably didn't help it. Help. please. Battery, starter?

Thanks

Here is some more info on my situation. I went back this morning to perhaps jump start it with some new cables. I thought mine were bad. It started to turn over a little bit but didn't start. Now its back to the clicking noise. Also there is a tapping noise around the glove box area when I turn the ignition. It last for about 10 seconds then goes away and when I turn off the ignition it does it again for another 10 seconds. Does this have anything to do with it? Should I run to Walmart and buy a battery? I priced putting in a starter at the mechanics $275.00 WOW. Please help.

Update,

Just went to Wally World and purchased a battery, hooked it up, no go. kinda grasping at straws. Desperately need someones help on this one. Is it the starter and if so, how hard is it to install? Again, I have a 94 chevy silverado extended cab v8, not sure of the size. no activity when I turn the key except for the 10 second tapping near the glove box area. Please help me. Thanks.