90 plymouth voyager sliding door won't unlock/open?

The lock used to be intermittent...it often took a lot of tries to get it unlocked, but it would finally open... now it has defied everyone and everything I have tried... I have the interior door panel off and have tried everything including a crowbar to no avail. Any hints from an experience (with this unit) mechanic would be great! The Chysler garage in town said they could do it...for $200! Do they know something I don't? or are they just optomistic? (dec 09)