OK, there's a lot of material here. And please note up front that I do not make any money from Musicians Friend, though I've bought a lot from them. They are an easy way to check prices and have a great selection. Be sure to check places like ebay, as you can get a lot of these things slightly used for great prices.
You might want to check out this mic and read the reviews. Though I have never used this particular one, as far as price vs. performance you will not see much better reviews without going higher in price.
http://www.musiciansfriend.com/product/Heil-Sound-PR40-Dynamic-Studio-Recording-Microphone?sku=271012Since you sound as if you are doing this from home, I would definitely get a large diaphragm mic. You'll likely be happier with it. And put a pop filter in front of it.
Also on that page you will see links to some articles that tell you all of the equipment you will need. It will tell you how to do a podcast, which if I'm understanding you, is about the setup you are going for.
Here are more choices which would serve you well:
http://www.musiciansfriend.com/product/AKG-C-3000-B-Condenser-Microphone?sku=271137 (I use this one.)
http://www.musiciansfriend.com/product/Shure-KSM27-Studio-Microphone?sku=270278http://www.musiciansfriend.com/product/R0DE-NT1000-Microphone?sku=271576Or for a really low end, you might want to look at something like this:
http://www.musiciansfriend.com/product/Behringer-B2-Pro-Condenser-Microphone?sku=270491http://www.musiciansfriend.com/product/MXL-MXL-V63MBP-Computer-Desktop-Recording-Kit?sku=273102Now from here there are so many ways you can go. Personally, as far as interfaces, I am a big fan of M-Audio and I use a 10 input/10 output system, though it does not sound like you need anything quite so complicated for what you are doing. There are lots of other good brands out there as well. If you don't mind living with two tracks, this unit is really slick:
http://www.musiciansfriend.com/product/MAudio-Fast-Track-Pro-Mobile-USB-Audio-MIDI-Interface?sku=241710It just connects up to the computer via a USB cable and that's all there is to it. Your voice transformer can be looped into it.
Here's some more interfaces:
http://www.musiciansfriend.com/product/Edirol-UA25-USB-Bus-Powered-Stereo-Audio-Interface?sku=705371http://www.musiciansfriend.com/product/Echo-Gina3G-PCI-Audio-Interface-?sku=700662As an alternative which will give you more bang for the buck, consider getting a mixer, which can indeed be hooked to your current sound card. Nearly all mixers have a left and right out. So you will need to rig a stereo connector
to your computer sound card's mic input from the outputs on the mixer. The mixer will let you control which channels go to the left or right. Virtually all of them nowadays have the mic preamps built into them and the specs will tell you how many. As with the standalone interface, your voice transformer and any other effects you have can be put into the effects loop.
One good low-cost option would be to replace your sound card with something like this:
http://www.musiciansfriend.com/product/MAudio-Delta-1010-LT-PCI-Digital-Audio-System?sku=701376Another option, if you have a firewire port on your computer, would be this unit, taking the place of the mixer and the interface:
http://www.musiciansfriend.com/product/PreSonus-Firepod-FireWire-Interface-with-Cubase-LE?sku=184131I also comes with Cubase, which is a decent recording package. Note that this is a rack mounted unit, so you would need a way to mount it, but you might do well to mount your voice transformer while you are at it.
Well we still haven't talked about mixer boards, cables, recording software, or speakers. But I haven't overwhelmed you, I'd be glad to talk some more.
Good luck!

Kristi