need help quick! 99 5.7L won't start

my 99 escalade (same as 99 tahoe for those who dont know) won't start. it makes a clicking noise when i try to start it (we think its the starter solenoid). tried to jump it, didn't work. checked the battery voltage, its at about 12. all accessories work. i drove it over to a friend's house, shut it off, then 10 minutes later we were ready to leave, but it didn't start. please help me out here!!!

First check the condition of the battery cables..make sure theyare tight and there is no corrosion present.
Since you say the starter clicks, then you are getting power to the solenoid from the switch...if the battery checks out, then most likely you will need a starter.

i was afraid of that. thanks for helping.

oh, and how hard is it to replace the starter on this engine? i have some buddies that are pretty good at engine work, would we be able to change it out ourselves?