Considering buying '05 ML350 - Anything to look out for?

[DonB]

We have a '98 ml320 that's been pretty reliable; worst problem was the anti-lock brake controllers cold solder joint (fixed that one myself, thanks for the help!). But it's approaching retirement age, so we came across a 2005 ml350 that looks good.

I saw some discussions about a balance shaft sprocket on the 06-07 ml350s that sounded kinda scary ($4000-$5000); does it apply to the '05? Also something about an air pump problem on an air suspension system; still not sure whether it applies to this model.

Anything else to be wary of?