Is it necessary to include drive gear for gear box overhaul

I have never sent the drive gear off when I've had my gearbox serviced. I just inspect it as per the manual to check for wear on the teeth.

No, I just had my gearbox serviced and it was not required.

I should add that I was confident I was getting a new gear set and dog hub due to excessive gear backlash and vibration while reducing power in the pattern.

Yes, you should send the drive gear with the gearbox so it can be inspected. The drive gear and the large gear are matching set, so if one needs to be replaced they both need to be replaced. Be careful when shipping the gearbox with the drive gear as we have seen that gear cause substantial damage to the gearbox housing due to poor packaging. 

Gearbox removal and replacement:

https://www.rotax-owner.com/en/videos-topmenu/elearning-videos/298-gearbox184

Locking Crankshaft:

https://www.rotax-owner.com/en/videos-topmenu/free-videos/245-lock147