I have the opportunity to FINALLY buy a HK USP .45, after a long wait for the money. This would be my first HK handgun, and I do not want to make a mistake. So what are the thing that I must know before agreeing to buy. I know there are different varients, but I do not know what they really mean. Also, are there manufacturing years more, or less desirable? I think I can buy the gun for $625.00, I think this is a good price, but I am not sure of that either. Any help would be great, Thanks.