the pump is below the reservoir in the space above the wheel, a bit of a pain to get at. You can see it if you remove the felt around the sele oil resevoir.
First de-pressurize, pull the relay and change gear, engine off, IGN on, until it can no longer do so. I found it easiest to take off the wheel and wheel liners, undo the front bumper bolts (two in the wing, the four at the top of the slam panel and a couple underneath should do it, that should allow enough movement to access the headlamp bolts and then be able to withdraw the lamp through the front with the bumper waggled out of the way. From there on everything is easily accessible. Drain the sele tank. undo the two hydraulic lines, undo the electrical connector and then the three bolts holding it to the body and its off. Then start to put in the new one.
A garage should do it in an hour if you give then that steer, its not hard, you may need a pipe spanner though if it hydraulic lines are really tight, but DIY-able. You do not need Alfadiag or anything either.