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.