From what I can understand, my mic, when plugged directly into the soudcard's mic input, would only send the Left Channel, and I would have to set the track's mic input to Left only
yes, but that's not a problem. that's the way it's supposed to work. your input is a stereo input, so you have to choose left only because your mic is a mono input.
but the project will put the mono mic input into the stereo field and output to both speakers if you choose the LEFT input when recording.
a microphone is a MONO instrument - stereo doesn't mean anything to a mono instrument unless you start changing the stereo field it's put into. you can do that by panning and adding FX.
So then, Beagle, my next question is; Would I still be better off going for a USB audio interface rather than analog?
what do you mean by "analog"? no offense inteded here, but I don't think you understand the terminology well. "analog recording" means TAPE. there is no other type of analog recording (well, you could use wax, but that's kind of ancient technology!).
My BEST advice to you is to get something similar to this setup:
http://www.musiciansfriend.com/pro-audio/m-audio-mobilepre-mk-ii $150
http://www.musiciansfriend.com/pro-audio/mxl-v63m-condender-studio-mic-with-mogami-mic-cable $100
there are other combinations, you could choose - that's just one that I know off of the top of my head that should work well.
as far as your mixer you were talking about earlier, you CAN use it even with this setup, but it's not necessary. if you want to use it, there are things you can do with it to help you with recording, but starting out and only recording vocals I wouldn't recommend it - just use the soundcard (interface) and mic like I have mentioned above.
even if you use your cheap mic and your built-in soundcard, you CAN use that mixer, but it's not necessary. if you use both inputs and the only thing you're recording is the microphone (mono) then you're going to put the outputs of the mixer into the stereo field, but panning will not work correctly because you're trying to pan a stereo track. it doesn't work the same as panning a mono track.
so again - my best advice is to get a traditional LD condensor mic and soundcard (usb interface) like I have mentioned above. if that's out of your price range, then use what you have the way I describe it above (input into the left channel only, record only the left channel and it will send the signal to both speakers from your MC project) until you CAN afford a better setup like I am describing above.