They certainly look like quality replacements but as you say....difficult to fit so may be easier to rub down and repaint the originals while still fitted to the mirror assembly
Maybe worth having a go on some smaller and easier parts yourself and at least that will cut down on the cost.
Seen it done and looked easy enough...although I don't think i would make a good job of it myself...no patience!
P13B6 BMW - Crankshaft Exhaust Camshaft Reference Angle Difference Outside Of Limit Value
Read more: https://www.engine-codes.com/search_codes.php?q=p13B6
Would check the timing belt / chain as if slack this could possibly cause this fault