Installing Dovecot is not that hard, but it does do a few things you need to be aware of. It replaces the vm-pop3d so, it handles both IMAP and pop3. It also uses Maildir instead of mbox, so all your mbox files need to be converted to the Maildir format.
The install of Dovecot takes care of that, but it has a few unwanted side effects, such as all the emails get marked as unread. This won't affect pop3 users too much, but IMAP users will have to remark all their emails.
Changes are also made to the /etc/exim.conf so that delivery to Maildir will happen, but you need to be aware of that, if you try to replace it with another version. You would need to make the Maildir changes to it if you upgrade it in the future.
Do a search for todovecot and it will show you how to install dovecot.