You can deal with hiss during tracking and/or during post-processing. Firstly, set up a gate which will "block" the signal below a specified level, so it will open when your voice is detected, and close as soon as you stop reading. You can also use some software or plugin to to get rid of the noise.
If MC 5 (cool abbreviation, BTW!) doesn't have any gate or noise reduction processing, look for free VST plugins on the web. There's tons of 'em.
First of all, you need to take care of the recording environment and equipment, though. In short - try to get as far as possible from your computer, other room would be the best, and get yourself a good mike. But it all depends on the target audience - if it's going to be your friends or family, the headset might do OK. If you're planning to be a so-called "voice talent", you gotta start thinking of some special place with lots of equipment for really big $$$.
