it could also be the antenna switch or the power amp.
how old is the phone and has the dropping leaved any marks on the phone ?
if you still have warranty and the phone has no signs of dropping i would try to let lg fix that problem.
it exists some kind of disassembly guide for that phone - but the picture quality is not very good and it's more for the experienced user
but you can take a look if you want: [http://www.howardforums.com/printthread.php?t=1481607&pp=15|CLICK here]