Custom module - change from autonumber to name

Custom module - change from autonumber to name

I fear I know the answer to this already, but thought I'd ask the question.

I created a custom module and instead of having a name as being the primary field, I changed it to an auto-number.  I didn't realise that all searches would only show this reference.  This makes it extremely hard to search.  It also means that you can't see which activities relate to which customer as the Related To is the reference too. 

I would like to change the primary field back to being a name, but I cannot find a way to do it.  Is it possible? 

If not, is there a way of cloning the module but with a new primary key, so I don't have to recreate the customisations?