Patches and discussion for Ensoniq VFX family

hi - 

i have an old vfx-sd, and it's great, but the battery has never been replaced.   i'm sure it's 
getting to where it's about to fail, so i want to be able to replace the battery.  but i have no 
info about how to do it.   is it even a DIY kinda job?    or should i trust a tech (if i can find 
one, that is!).    please post any links for information, etc., whenever you get a chance out 
there

thanks!