From where is it leaking - input or sector shaft? Somebody on this board recently rebuilt his steering gearbox and maybe he could tell you what size seal it will take. Unless you've got a lot of miles on your VX or you've fed it dirty fluid, it's probably just the seal itself that's worn. You don't need to spring for an entire new box - just yank the old leaky seal out and pound a new one in using the proper size PVC pipe or something similar. 10 bucks and an hour of cursing and you're leak free again.

If you want to replace all the whole gearbox, Advance Auto, Auto Zone, etc sell rebuilt units for $350 or so and will loan you a Pitman arm puller.