What you have is a set of OZ split rims produced for AMG by OZ racing.
The nuts can be bought on eBay.....if you're going to the time and expense of replacing them I suggest you buy stainless steel ones, don't skimp on the nuts either...
Unlike BBS split rims I'm reasonably sure you can use a high quality (Snap-on or similar) 8mm socket to remove the studs, but do check this...it may be duff advice.
These are three piece wheels, but the centre section is not actually sandwiched between the two rims, the front and rear rim are sealed together, then the centre is bolted on the back.
This has the advantage of being able to unbolt the centre without having to break the airtight seal of the front and rear rim for a repolish. However, I would probably split them right down and get he whole job done properly and a new seal put on.
A word of warning, these wheels have a tendancy to develop hairline cracks by the main 5 bolt holes, so it's important that these are never fitted to the car with an air gun, always tighten by hand.
Also they always left the factory with the air valve fitted directly opposite the AMG logo on the wheel face, not next to it, or at a slightly skewed angle.
Oh and get some decent chrome or stainless valves for the rebuild...black rubber look awful after you've gone to the expense of polishign the rim.
Chrome bolts:-
HERE
A wider variety here:-
http://www.tunershop.co.uk/Wheel_Accessoires/Rim_Screws/?TSID=7da7db51e51297600fef694c7c2fcb8b
Just out of curiosity, I sold a set of these to a chap in Ireland last year for his W124 coupe....this would happen to be you would it?