Not a difficult job at all really. You can make it easier by putting a jack under the crankcase and removing the big engine mount bolts either side, then lowering the engine by a couple of inches.
There isn't really an 'upgrade' to be had with diverter valves. They either work or they dont. There's no performance enhancement. I use the audi RS4 Diverters in mine, £50 for the pair, exactly the same part and do the job.
The N75 is easy to do if you've got some snipe nose pliers. Once the airbox is out of the way, engine lowered, bit of space by removing the F -pipe (not necessary to do but can help) then its just a case of removing the hoses and the connector and swapping them over.
:thumb: