Yes, very easy.  Couple things to think of before bidding:
1.  Payment options....some only accept certified check or money order.  Some charge 3% for credit card.  Just make sure they take payment you are willing to use.  Some sellers are now using the gun broker paying gateway. 
2.  Make sure it is a verifies seller and they have plenty of sales. Also make sure they have good reviews. 
3.  Look at their shipping amount.  Most are very reasonable and a few are ridiculous.  
4.  You can always ask questions before buying.  If a buyer doesn't respond to my questions, they lose my business.  
If you are smart and take standard precautions, it is very safe and very easy.