Technically you can't sell the .IE, but it can be part of the sale.
Basically to sell a site you need to
1) find someone who will buy it (most people fail at the first hurdle)
2) if they already can lay claim to the name, then skip to part next part, if not they will need something, either you change the business name to theirs or get them to register another one.
3) file a request with the
IEDR to get the claim to the domain changed
That's it, there is more steps in case they don't want to take over your hosting contract::
To move the domain to another server, if they have one of their own already
4) download everything from the old server and upload everything to the new one.
5) change the
DNS settings to point to new server (and domain name servers)
6) take down the old site when you are sure it's been transferred
7) cancel your hosting
Live in peace.