I would not replace the solenoid. I don't think it is a common point of failure. The seal around it is easy to swap out. Just 2 bolts. Removing the solenoid actually takes a special socket if I remember correctly.

Beisan Systems has been a big help for me. I have rebuilt the vanos units on both my M62 and M52TU engine in my E39. The V8 (M62) is a way bigger job as the cams have to be timed, etc.. But I was there anyway doing the cam chain guides.

__________________
2001 X5 4.4i Sport
2013 550i Xdrive M Sport
2000 528i E39 (Sold)
Unleashed Air Racing 279 mph Best Average Speed