Hi D. Tuna,

Thanks and welcome. And welcome to the world of acoustic blues guitar, you couldn't have made a better choice. As to your question on Stefan Grossman, who will be playing at Eric Clapton's Crossroad Blues Festival in Chicago this summer, he is in my opinion the greatest resource for info on the history and playing techniques of the various folk blues traditions and even into some of the early electric artists.. and there is Celtic, country and other popular styles covered in his many titles on dvd. He has a series of 3 dvds called "How to play Blues guitar" that I like and it has the original recordings included as source material. That is at a level 3 of 5 , so it's going to depend where you are with your fingerpicking technique. He has more and less difficult lessons available, you can also view the sample lessons to see where you'd feel comfortable. Taking the time to master basic techniques will pay off big time as you get deeper into the material. Once you master the basics then you can add in many of the musical ideas I'm sure you have learned over the years. Blues has always had a large element of improvisation. Hope that's helpful and I'd be happy to answer anything else.
Also let me recommend a book to you , called "Chasin' That Devil Music" by Gayle Dean Wardlow which is a comprehensive history of the Delta Blues.
'

Pete Gallatin
http://www.reverbnation.com/patiopete