Help with Lightroom/file sizes!

I just started out as a hobby photographer so forgive me if I don't know the basics. I work with Lightroom 2.0, and I am having problems with my pictures being extremely smaller after I edit and export them.

The pre-edited images start around 2 MB and then after editing in lightroom they are 200-300 KB. I'm afraid at that size they will be blurry if blown up. Is there a setting I change on my camera or in Lightroom to help? What quality would you recommend shooting in? I've been doing friends weddings and I don't know which setting is best to get a good picture but not be too large, etc. I have a Canon 30d. Thank you so much in advance for help with this.

When you export make sure you don't have the Image resizing option on, set the quality slider to 100, and use sRGB as your output profile.

THANK YOU THANK YOU!

And download the update to version 2.3 - there's a lot extra from 2.0 that you should really like.