Three 12-hour days is about enough time to completely finish one song. Plan on spending around 30-40 hours per song, including time spent mixing and mastering.
Before you go in, be sure and have everything down 100%. You need to know EXACTLY which songs you're gonna record, EXACTLY how you're going to play them, EXCATLY how many guitar tracks you're gonna do (you should do at LEAST 2 tracks for every one guitar part), etc. Make sure your drummer cleans and tunes his drums the day before the session, and by that I mean make him sit down, take everything apart, clean everything, lube all the nuts/bolts, and spend time tuning each individual drum. If you get to the studio and they tell you 'We've got drums already set up, and they sound great, leave your drums in the car and use ours', take your money back and leave. Same thing goes for guitars. Well, that is, unless your drummer is playing a CB300 kit with tinfoil cymbals, and your guitar player has a balsa-wood Samick. At any rate, you're gonna get the best feel out of whatever you're used to playing on. If you have to play the song 30 times to get used to a new setup, that's money and time that you're losing. Plus, if whoever is mixing it is worth a shit, he can pull a good sound from almost any drum.
Which brings up something else....when you say 'the guy who did evergreen terrace's first cd', what did he do? Produce? Mix? Master? Track? If someone introduces themself to you 'Hi, I'm the guy who did so-and-so's first cd', that could very well mean 'Hi, I set up the microphones and plugged in the headphones when so-and-so recorded their first cd'.
At any rate, have fun, and take your time. If you're rushed to get in 3 songs, the songs are gonna sound rushed. The more time you spend now, the better you're gonna like the final product later.
Enjoi!
edit: And before someone comes out and says 'shut up, you dont know what you're talking about, blah blah blah', I speak from experience. My dad owns a recording studio here, and I've worked in it since I was 12. The chief engineer here (Tom Pierce Baker) tracked & mixed Pantera's first 3 cd's, and I've learned pretty much everything I know from him.