Idler pulley bearing question?

The pulley has been removed. So, the question is when I purchased the new idler pulley the inside bearing is sealed. And the hole is without the race pulley and bearing only. It cost $28.00. Is this normal protocol will the race from the original Nissan pulley work? It appears to be the same identical size. It will fit into the new bearing. Used a socket it come right out of the old one. This is a two-question message. About the nut that holds the pulley on is missing from the bolt. Will a # 10 nut 1.25 pitch be safe to use a long with thread lock? Thanks. JC