permalinks error – preview error – image errors

here it goes..

i installed wp 3.0.2 into a folder example.com/WP
then i bought a domain mydomain.com

i changed the site address to mydomain.com but the wordpress address stayed the same example.com/WP

im having some trouble with permalinks, i had to change the .htaccess manually and upload it.

permalinks are with month/day/post name

here are the main problems.

when writing a post i can’t preview the post, it gives me 404
the preview address is mydomain.com/?p=189&preview=true

at the time of selecting an image, the image stays with the old address example.com/WP/

if i change the wordpress address, images wont work (is there a fast fix for this… i have around 50 posts already and changing them one by one its kind of tedious)

what’s the best way to fix these issues ???