Re: Fly Fishing Maryland
I've been working thru Gelso and Coburn's great book - Guide to Maryland Trout Fishing - it has great info, maps, recommendations, etc. It will put you on the right track.
I recommend you also do some generic searches - you can find a lot of info right on the web. For example - do "north branch" trout for the North Branch of the Potomac or "Hoyes Run" trout for the Yawk, etc.
Getting the book puts you on the right track.
In terms of fly shops, they are getting scarcer - I recommend you just click on some of the sponsored links on this forum to get your gear.
The recommendation on TU is good as well - many of the TU chapters have fish with a member trips that will put you in the right place at the right time.