Vintage Synth Repair

hello freaks,
i just bought an arp odyssey III synthesizer in a good cosmetic condition.
the problem is, the owner hasn't played it for about 20 years.
so there is just a lot of dust and some sort of oil in the sliders. many
of the filters don't work, and everytime i turn it on, it sounds quiet different
from the last time, but i didn't change anything. i allready cleaned it a
bit, but i cant' get into the sliders.
however, there comes sound out of it, so the basics are working.
it's quiet difficult to find an synthesizer-expert here in switzerland, so
i just thought i will repair it by myself.
what do you think, is it possible? what would you recommend me to do? any
tips or instructions? 
i would be very pleased for help!
thanks a lot

sevi