Combining two coop apartments

My neighbors want to sell their one-bedroom apartment, which can be combined with my apartment. We think that the only work to be done would be to break through some closets; it looks like their apartment and my apartment share two back-to-back walk-in closets and to get rid of their kitchen (as their kitchen is very small). What do people think it will cost? Once the closets are broken through, the floor portion in the closets will need to be patched up too but otherwise, there would not be any further change to the floor plans. Anyone has recommendation for an architect for a project like this?