Alex,
You stock ride height will stay almost exactly as it is now as long as you abide by the Plus 1 rule which is: The aspect ratio (sidewall height)of the tire goes down one size as the wheel size goes up one size. If you had 16" wheels and going for the 18", then go for the Plus 2 rule.
Here's a link to explain it a little better.
http://www.kaltire.com/retail/custom...lus_sizing.php
P.S. No stupid questions here. Way better to ask what your not sure of than to find out you've screwed up after the fact.