Mounting a 50" Plasma above the Fireplace and I've hit a wall! (pun intended!)

Hi there,
I am thinking of mounting a 50" plasma above the Gas fireplace. Including the bracke the total weight would be 165lbs or so. There are a couple of 2/4 studs which I can hang this on. I am stuck half way through the process - would greatly appreciate advise from the experts here.

1. I drilled hole deep enough for the bolt on one stud at the level I wanted. However I hit some kinda metal plate after one inch on the second bolt. What should I do ? Keep drilling through or try drilling at another level ( which means the TV wont hang at the ideal height)

2. Can the two 2/4s carry 165 lbs of this huge Plasma TV and heavy bracket?

3. I have tried with a couple of stud finders but I seem to get different reading every time I try to locate the studs. one of the 2/4s (whey I hit the metal plate shows 1 1/2 inch at times and 2 inches at others. I got a brand ne laser level and stud finder for 50$ and although I follow all instuctions (wait for caliberation etc) it beeps continuously at times or gives me varying readings. Is there a conclusive way to find out what is behind the dry wall above this Gas fireplace?

Sorry too many questions here but hope you can help and get me out of this bind I'm in!

Many thanks in advance.

not recommended temp over 300 degrees comming from circuit boards.heat from fire place will melt the chrystals inside schreen. shorten life to tv schreen.

thanks for the reply! but I wont be using the fire place. I have central heating in any case. So can you help me with the questions about studs n weight etc?

the metal plate might be part of the fireplace.

ok saw this on TV the temp above the fireplace should not get hotter then i think 90 degrees. stick a thermometer on the wall over the fireplace while the fireplace is lit and see what the temp gets. 90 or under your fine.