Welcome to OCDO!!! Stick around an you will learn alot!!!!
Yes, it is legal to buy a handgun at age 18 from a private seller. It is also okay to OC said handgun. I will look up the cites when I get home unless someone beats me to it. If you conduct yourself in a professional manner, you should not have any problems with an LEO. You can carry a copy of the relevant laws until you feel comfortable reciting them from memory. Also get yourself a good recorder and keep it on anytime you are carrying.
Check out the Virginia Citizens Defense League. It is a great group dedicated to gun rights in VA. If you go to their website you can sign up for VA-ALERT (on the right side of the page) which is a free email system that will keep you informed about everything gun-related going on in the state. The website is http://www.vcdl.org
Also check out the Virginia forum here.