Removal of bridging unit

Hi

I'm looking to replace the doors on my kitchen. I've found a cheap lot for sale - don't want to spend a lot as only changing due to my ex-tenant trashing my current kitchen doors. Fablon everywhere including the worktop

However, my problem is the doors I've seen don't have a a bridging unit. How easy is it to remove the carcass from the middle of a run and replace with an extractor/chimney?

Cheers.