The original front hub cap is plastic and with the Mercedes logo is readily available, on Ebay or elsewhere.
Sprinter front hub cap
Your wheels have a split, conical washer, under the lug nut. When you install these, you remove three lugnuts but leave the conical washers in place. You then place the hub cap on the studs, with the hubcap's three embedded flat washers on the three studs of the lugs you removed, on top of the split conical washers, then you reinstall the lug nuts and torque (gingerly) to 133 lb/ft (which is a lot for such a small stud).
This still leaves the lugs themselves showing, they are a 19mm hex and you can buy silver or chrome lug nut caps on Ebay also.
Chrome lug nut covers
The tool is handy to remove them since they are recessed in the hub cap.
I installed the hub caps on the front of my '07 View, but never did install the lug nut covers.
The black mercedes hubcaps used to be cheap on Ebay, because the motorhome companies, when they installed the simulators, removed the OEM hubcaps and the employees took them home and sold them on Ebay. Now, the motorhome companies have found that the simulators will go on right over the plastic hub caps, so they do not bother to remove them. Go find a new sprinter chassis motorhome with simulators and remove a front one, you will find the OEM black plastic hubcap underneath.
As for the rear, there is nothing sold for those as Mercedes never fitted the rears with any kind of hubcap. One person on the View/Navion forum on Yahoo took a pair of front covers and cut a hole in the middle so they would slip over the axle hub. Paint the hub black and it barely shows, the rest of the cap covers the lugs and it looks somewhat like the front.
Many people install the Borg stems. I had no luck with them, as they didn't fit properly and made the rear wheels extremely difficult to install without damaging them, as the outer wheel has to be slipped over the stem of the inner wheel, without bending or breaking it.
For service You will want a long stem tool such as this Milton S693-12
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
It has locking grooves inside the ends of it to help it "grab" the threads of the stem so it doesn't come off easily. I did not like this so I changed out the end nuts for smooth ones.
https://www.miltonindustries.com/dua...chuck-nut.html
For a gauge, you need a similar, straight/angle foot design, many of which are available on Amazon.
Charles