How to clean up messy geometry from a file?

 From:  Chris (CHRIS_C)
9208.1 
Hi folks. I was given a file to 3D print and it is "messy" to say the least. The original file was lost so this is the only file available.

I have uploaded a similar part I created in Moi to demonstrate what it *should* look like.

How can I clean this up without losing the very specific shape and size? Suggestions for rebuilding also appreciated.

Thanks

Chris