Finding my way around Philadelphia

Hi folks. I'm traveling to Philly soon for business. Taking Amtrak from CT into Philly's 30th Street Station. For the life of me, I cannot figure out how to use the map on the SEPTA on-line system. I'd like to be brave and use public transportation (no cabs) but I feel like I have no idea what I'm doing. Can anyone help?
1st I need to get from 30th Street Station to Spruce at 12th. Then from there I need to get to the Convention Center. And of course reverse of all that at the end of the day. Can anyone from around that area give me some advice on the subway, or some other method of public transportation?
And, of course, will I be near any incredible not-to-miss food places?
Thank you all so much for any help you can offer! :)

All I can say is do yourself a favor when you are on your way back before you descend back into the subway at Spruce and 12th, find your way over to Monk's Tavern, and have a Hoegaerden with some Pommes Frites. It will make your entire trip.

I sure will. And thanks for the suggestion.

While I'm at it...has anyone recently been to Lorenzo's Pizza and had a cheese steak? My co-worker LOVES the description of it here on Roadfood, but I'm not sure. It certainly looks very cheesy, but I'm not sure that lots of cheese is necessarily good. But I do like the idea of chopped up steak vs. whole "slabs".

Go have a cheeseseak at Steve's Prince of Steaks before you turn away from so-called "slab" cheesesteaks
http://www.hollyeats.com/StevesSteaks.htm