Cracks across the belt are normal but if it hasn't been changed in a long time & you are going to remove it anyway to work on the engine then do it.
No I didn't change mine, are you sure the harmonic balancer is wobbling? A dirty HB can look like its wobbling, degrease it & give it a clean & then check it again.
Part number for the HB is
68056244AA
http://www.usautoparts.com.au/Store/Product/?id=5063
http://www.genuineautoparts.com.au/j...bration-damper
eBay have cheaper ones listed.
A great how to for the belt
http://www.chirpz.com/jeeps/belt/belt.html
Water pump P/N
68047688AA
I used a Tru-Flow brand as I could get it in Australia & it has a 2Y warranty.
P/N TF8431 The box says made in USA but it had made in Germany on the pump.
The one I ordered
http://www.ebay.com.au/itm/Water-Pum...item3cf607b656
This site has a list of aftermarket pumps.
http://www.yoyopart.com/oem/5781582/...8047688aa.html
Mercedes Benz original P/N
642 200 07 01
The Belt I used
http://www.ebay.com.au/itm/7PK2035-D...item4aece5d958