>What type of fuel consumption is associated with an ML320???

It is heavily dependent on your driving style. I've got accurate numbers on the ML430 using US gallons:

City 16 mpg
Hwy 55mph 20 mpg
Hwy 65mph 19 mpg
Hwy 75mph 17/18 mpg

Towing I don't remember exact figures but IIRC the worse number was 12mpg towing 3 tons @ 75 mph. Towing 1-2 tons @ 65 mph was in the 14-15 mpg range.

The 320 should get anywhere from 10-15% better assuming the exact same driving style. But to give you a comparison on driving style effects my wife drives like a NY taxi and gets at best 14mpg in the city and 5-10% worse on the highway.

> Also, how can I tell that the "Harmonic Balancer" has been replaced?????

It should have been done under warranty if it occured. Get the repair history from the owner. You can go with the owner to his/her dealer and get a printout for free.

> I also ran across a thread about an "electronic box" that cost a whopping $5,000.00 to replace (dealer item only).......Honestly, in these economic times, I do not want to bring a "money pit" into my life.....

There are four electronics parts that are an issue. The first is the module security module that "approves" the key. There are a limited number of keys that can be activated in the early models (8 if I remember correctly) and once you reach that number you have to buy a new module that is only available from the dealer and can only be activated by the dealer. The electronic portion of the key fob so far lasts forever unless physically damaged. I've even left them and the pants where they got washed with no damage. As long as the current owner has only activated a few keys you should be fine. If s/he is nearing the limit I would not purchase unless you have a, well, $5k discount.

The second issue is hooking up jumper cables the wrong way (positive -> negative and vice versa). This can fry a lot of expensive parts.

The third issue is spilling a drink down into the insides of the center console. There are electronics in there that are not water tight.

The last issue is the ???? plate in the transmission. These have gone bad. But the total repair is under $1,000 and appears to be a one time item. It isn't common but does occur and should be noted if one day your transmission fails. Instead of a $2,800 repair it could be less than $1,000 at an honest shop.

The last item is really the only thing that I would consider a "gotcha" as the others are all under the control of the owner.

>(I was an ASE Certified mechanic for a little more than a decade from 1987-1999, though never a Benz tech) so I'm wondering if my skills would save me any huge repair costs on an ML class

Yes! The repairs are for the most part very simple. This is IMO the easiest vehicle in our fleet which consists of domestics and Japanese in addition to the MB.

> but a $5,000 part would be the kiss of death for me!

Other than the issues mentioned above the electronics appear to be quite robust. Other than that transmission issue I've read of darn few problems that were actual part failures and not caused by the owner. This is not to say that there haven't been a lot of parts changed out. There have. But if you read the case histories you'll find that it is the dealer either doing "guess and replace" or not taking the time to diagnose the actual cause which is often a cheap and quick solution. One problem that does occur is if the seals on the harness connections fail or water starts dripping on the part corrosion at the connection can cause an apparent failure. But the actual solution is to just clean the connection and make sure that it is water tight in the future. ABS systems and the connection to the transmission are the general culprits here.