You would be better server to draw your interfaces in like fireworks or another true graphics proggy. Flash was not intended to do major drawing thus lacks some of the finer tools. You can imprt your graphic into flash. That is how most sites are built.
NP…you can import in as a .png so basically it will be compressed 2x. You should be ok with the file size dependding on your graphic. www.phong.com and www.voidx.com have some sweet techy interface tuts.