I wouldn't worry, if they want to fit a part from their supplier then they have to warranty the job, a condenser is the kind of thing that will fail within days or be good for years (or longer than the useful life of the car) so unless you want to keep this 9-5 forever and keep it fully genuine I'd let them fit what they want, it's not quite the same as a moving part or electrical item. If you ask them to fit your parts and the part fails they won't be interested in swapping it again for free.