Okkie,
some good advice from Robin for you.
I had been looking for an old BOC Falcon manual that I used to have but cant find it anymore, must have been recycled. This might have given me the original gearbox specs. Removing the CMC 2.5 and the HL90 might be your best option in the long run. The Burny is a good little controller for a low cost machine, pity about the lack of graphics though. You needed a Burny V or 10 for graphics. It understands G code, Word address and ESSI files. Nice package in a small box.
If you down the PC route as you say once you have drawn up your parts they are easier to store for future use. One benefit you will have is if your customers can supply you with a ready made cad file, this would just need checking then off through the post processor and your ready to cut.

Ian