Change from POP to IMAP in Mail

Hey, I currently have a POP account setup in Mail that I've had going for years ever since signing up to .Mac (now MobileMe). This was fine as I was quite happy to download the mail straight to my Mac and not have a copy left on the server.

I have since had an iPhone and am thinking of getting an iPad, so would like to switch my account type to IMAP so that everything stays in sync. Is there a way to change the account type from POP to IMAP? I'm assuming if I delete my POP account and setup a new IMAP account from scratch this will delete all my inbox, sent and trash items for the current POP account?

Thanks.