The clicking could be normal relay clicks, don't be in a hurry to fix it if it ain't broke.

Before anyone can give you 'the fix' you must describe the 'faulty heat and air' in a lot more detail, such as outside air temp, inside temp setting, which button is pushed, where air does/does not come out. There are several ways these systems can malfunction, and some normal operations that are not completely understood by new owners.

That said, welcome aboard, you've come to the best forum for M-B related help! Also, do join us in Diesel Discussion (right below Tech Help) as there a lot of diesel fans there.

Best Regards,
Jim