Check out these articles for diet advice geared towards putting on quality mass.
Get Big Diet -
http://www.T-Nation.com/readArticle.do?id=459756
Massive Eating by Berardi - essential reading.
Pt 1
http://www.T-Nation.com/readArticle.do?id=460331
Pt 2
http://www.T-Nation.com/readArticle.do?id=460327
And here’s an awesome thread with fantastic recipes so you don’t get bored eating tuna out of the can -
http://www.figureathlete.com/readTopic.do?id=1498939&pageNo=
Make sure you stick to the big lifts - compound movements. Bench, squat, deadlift, rowing movements for back - these will help you put on the mass you’re looking for.
Use the search function because everything you ever needed to know is here on this site. Just don’t get overwhelmed by it all. Keep it simple - eat big, lift big and consider some solid supplementation - fish oil, aminos and a good protein powder/meal replacement.
Best of luck…