It depends. Are you comfortable working on electronics? Do you have a multimeter?

Start here:
http://www.pinwiki.com/wiki/index.php?title=Bally/Stern

If you are in a hurry and have the dough:
http://www.allteksystems.com

I've gone both routes with repairs. Some of it depends on skill set and time. Some of it depends how far the corrosion has spread.

Whichever way you go, the first thing to do is remove that battery from the board

On the coin door is a latch on the right side

Move it, then remove the long silver lockdown bar at the front. ( it lifts straight up)

The glass now slides out the front, and then the playfield lifts up.

There should be a bar on the right side of the cabinet that will keep the playfield up.

And it's hard to tell, but it looks like the battery has already been moved off the MPU board