Advise on Mastering Vocals

[proactive]

We are a not for profit spiritual organization and cannot offered to go for professional mastering. We record strictly male vocals in a semi-studio setup (sound proof & acoustic treated). We have only one speaker and we don't even add music. We are able to record fairly well.

NOW - please advise how to do the mastering, to the release quality. We do not sell the disks/audio material but do play it to groups of audience and want to give them the best experience. So, any detailed explanation as well as relevant links are greatly appreciated.
BTW - how does normalization improve audio quality; or does it create any problems.

We use Sonar 4.0 with Digi 002. And we need to ensure that the audio does NOT change in anyway from the original recording, even if it sounds better. Thanks.