The hardest things for recording in this situation, in my experience:
Micing and Recording the drums properly. If you are looking for Commercial CD quality, with live drums, then you must do this right! Believe me, this is the main thing holding me up with the stuff I've done. That and working with the tracks afterward to try and get a good sound mixed.
What Undadogg said about wearing two hats is right on. If you are going to be a singer/musician on the recording as well as engineer. . . good luck. Oh it can be done, but you said your goal is commercial quality? It's very hard to give the attention to detail of proper micing and gain staging, and avoiding peaks, and all the other things when you are also trying to perform with excellence!
I don't care how much you spend on equipment the important thing here is knowhow. If you have the budget for a lot of great equipment by all means don't skimp! But that alone will not be enough. If you want to do it all on your own then I hope you don't have a day job, because you will need to eat drink and sleep recording for a fairly long time to get in the trial and error experience that you need to get what you are after. Even then, by the time you get done with your last song on the project you'll want to start over and re-do all the stuff you now know you did wrong!
My church is set up great for live sound (if I do say so myself) but not so great for recording. Recording our services is not a high priority at this point for us, as long as we can make decent tapes of the Sunday messages, that's all we need. I had brought in my set-up from home to record when we tracked there. We are in the middle of relocating our mixing to the floor where it should be

(thanks to me as well

) .
You will probably want 2 mixers and a signal splitter, because you will need to mix the live room as normal, while still recording in your isolated location. If you want quality this is critical, especially going live to 2 tracks, you don't get a second chance. Here also is where it is important that the singers especially can hear themselves well. This is the biggest ongoing issue with our group, when we play back the service tapes of the music, people are always off key, and or not enunciating well. In fact when you finnaly do your live multi track, you may only want to record the lead voices, making sure they can hear really well, and just go back later for all back-ups choir etc.
all I have timew for ahorita!