I had something very similar on my 145 and I suspect the 156 will be much the same. It was an easy job. Popping off the interior trim was the hardest bit. The motor was just seized solid when I got it out. I swapped it for a used Ebay one.
Might be worth dosing it with WD40, once it's off - if it's seized, I think that's likely to be mechanical rather than electrical, & won't cost you anything to try. It may have blown the fuse, though.