I am just about to start making a sybian for my girl. It doesn't look that hard. I recently made a fucking machine using the instructions posted here:
http://unsafewords.com/?tag=do-it-yourself. Because I already had a sawsall and speed controller, that was a cheap build (like $20 for the dildo with vac u lock base).
For the sybian, I'm going to build the base out of plywood. And I'll cover that with upholstery foam and vinyl. To power it, I'm going to use a jigsaw mounted upside down.
I'll take a jigsaw blade and grind off all the teeth. Then drill a hole into a dildo vac u lock base, and epoxy it in place. It's important to leave the blade long so that it can accommodate the full stroke of the saw without drawing the dildo base onto the saw and tearing the whole thing apart.
And I can't stress enough the importance of a speed controller. These things are cheap, available at any Harbor Freight store if you have one in your area, or from their website. No woman can handle one of these motors on full blast.