Just Checked, New Vito (639) has same adjustment system - 2 bolts, slacken one, adjust other (cam bolt)
Both types (638 & 639) knocked out of alignment and camber by potholes / rocks in road,
If you look, the bolt head has a "cam" just under the hexagonal bit and there is another "cam" washer under the nut.
OF COURSE mb said you can't do it as it needs specialist equipment, hence THEM and a lot of money.......... a 4 wheel check from MB is quoted as £350 plus vat plus any additional costs (time) if they adjust anything.
NOTE MB don't do it themselves but call in a specialist firm.
However with the angle known (consult WIS with your vin number) you can put an inclinometer on the wheel (or support the wheel hub at road height and attach the inclinometer to the brake disc for better access) slacken the bolt on the bottom of the leg and adjust the cam bolt; when the inclinometer is at the correct reading, tighten the nuts and recheck (in case it moved slightly)
I got an inclinometer (digital spirit level) on ebay for £18 from hong kong (10days delivery) and they are easy to use on a level driveway.
To level the wheel, measure the centre from the ground (accurately) remove the wheel and support the hub on a stand or the like at the same height from the centre to the ground (I used a building block and a couple of bits of wood) although you can do it without removing the wheel, it does make it easier.
Last Beer 16 feb 1989............. if someone tells you when they had their last.... it WASN'T their choice.