I saw them in November and will be seeing them in July as well. Right now they have this mandolin player named Eric Mittendorf ( I am pretty sure that is the name but you can check the Tuna web site to check) and he is amazing. He solos on the thing lik it was an electric guitar, it blew my mind. But the shows were awesome and so were Jack and Jorma.
As for starting with Hot Tuna, you should just get each album from the beginning, they are all good. Defiantly start with the acoustic though, I like it better than the electric persoanlly. My favorite acoustic song that they do is probably Mann's Fate, so if you can find that, I think you will like it.......Jack and Jorma play really well on it.
If you were a cloud and you sailed up there,
You sail on water as blue as air;
You'd see me here in the fields and say,
"Doesn't the sky look green today?"