Copying records from a Custom Module into Deals

Copying records from a Custom Module into Deals

Hello, 
I recently created a custom module to handle a particular type of order/transaction in our business. Having got this up and running I've realised that it would be much better to use the Deals module with a different layout instead. We've entered about 40 records in the custom module, including subform info, notes and attachments. 

I now want to copy all of those over to the Deals module, using the new layout. What is the quickest/easiest way to do that?

I planned to export the custom module records into a csv and then import them into Deals but I've realised that the notes, attachments and subform info have to be imported/exported separately. So, how do I make sure they're connected to the right records? I feel like it shouldn't be too hard but I'm not confident about that part.

Any tips and step by step advice would be greatly appreciated!

Emma
PS. I appreciate that the number of records isn't massive but knowing how to do this confidently could be very useful in future!