Jim, there is a website called 'The Singing Voice', which has history of singing, other interesting topics about singing, and under the heading "Pedagogy" is a page called 'Vocal Health' that has tips on how to take care of your voice.
http://www.geocities.com/Vienna/Strasse/2200/

Knowing techniques for warming up, placement of the muscles, how to relax, etc. really helps, no matter what style of singing you do.
If it seems like you have really changed your voice, you may want to see an ENT who can examine your vocal chords.

alice, mt