I've never recorded a full song in a non-studio environment before, but I know I need an interface for decent quality. Does the interface emulate an amp, or do you put the guitar through the amp, then attach it to the interface? Can anyone recommend one?

Thanks much.
I would recommend the Presonus Fire Studio. It has 8 preamps but is a 26 in and 26 out interface. Meaning, you can daisychain multiple preamps together to make 26 inputs and outputs. I dont know if you ever need that much but...If you do you have the option right. As far as your question you can run your guitar through a DI or if the interface has built in DI and then run an amp simulator plugin or you can mic up your amp. or you can run into a Di then use the thru to go to your amp so u record the same thing one amp one Di then duplicate the di and run multiple amp plugins to mix up a guitar sound. I read on the new AFI album they used 3 different heads to achieve one sound so just some food for thought. Got any more questions just hit me up.

Recording Engineer
and if you DON'T NEED a $500 interface for a whole band then I'd recommend a Line 6 GX 1 or UX 1 or UX 2. I use a Boss GS-10 USB Interface and it works beautifully - I recommend it to everyone but they are no longer being produced - Ebay only - the Line 6 ones are really nice - not REAL EXPENSIVE and come with some nifty amp simulators called Pod Farm - great for recording.
Now running an Eleven Rack with Pro Tools 10.3.3 - it's amazing and I'm having ball with it - worth every penny. PT 10 is tops IMO and the Eleven Rack is a work of art!