Sorry if this info has been posted previously and I missed it - for those needing or looking to replace the glider servo, a digital variety will work just fine. In other words, the replacement does not need to be analog.
I just installed a HiTec HS-7955TG servo and its working just fine. The benefit of a digital servo (at least this HiTec model and several others), is that they're programmable and its rotation can be reversed via desktop software - instead of having to mess with reversing wires by solder/wire cutting.
It'll cost a few more pennies, and this model is totally overkill for the application, but i got sick of messing with small motor skill stuff. And, I guarantee this little black box will long outlast the machine itself.