Account wise, you could sell the account however the original owner may get it back and and then you will be in a pickle with the person you sold it to asks for their money back which you may or may not have at the time. Also, people are more reluctant to buy it if you have merged it with a battle.net account if I remember correctly so not really a good idea to do that.
If you wish to play on the EU realms to check the account all you need to do is simply edit your realmlist.wtf in a text editor or equivalent - which is located at C:\Program Files\World of Warcraft\Data\enUS. As your US you should probably see:
Just change it to...Code:set realmlist us.logon.worldofwarcraft.com set patchlist us.version.worldofwarcraft.com set portal us
Now your able to log onto the EU realms. Just remember to switch them back when you want to play on US realms again. Peace.Code:set realmlist eu.logon.worldofwarcraft.com set patchlist eu.version.worldofwarcraft.com set portal eu