when you say damaged, in what way ?
As long as the inside bore is still smooth, the barrel should be fine.
Buying a barrel is all down to personal preference.
You choose between wieght, sound, and bore size. There are other options like length or wether you want a one piece or two piece. Also consider barrels whereby you could change the inserts or the backs if you want at a later date if you have more cash to spend.
Weight : carbonfibre barrels are lightweight, but can be louder.
Sound : A barrel with more porting = quieter (no porting = cannon)
Bore size : I personally would have between 0.688-0.692 (size of paintballs are commonly between 0.684-0.688 lately. A good bore to paint match = more accurate also better on efficiency.
Length : Most common 14inch although there are a few players like to use 16inch. (no difference in performance apart from the extra 2 inches further
)
Two piece : you might have the option to buy a different size back, unlike a one piece. (different front if Un1tec barrel)