thoughts on the ML320 ?
Sorry about that, it has 160,000 miles.

Don't listen to stories about high cost of repairs. Of course the cost will be high, if you need to fix a bunch of things, but if a Mercedes car is maintained the way it should be, it's not much costlier than any other car.
Make sure YOUR Mercedes mechanic looks at the car you want to buy. If the seller doesn't want you to take the car to YOUR mechanic, walk away!
I have a 2000 E320, which I bought used. The previous owner took very good care of it and I do the same. If you were buying this car from me now, you'd think it was a new car (I'm not selling, just an example.)
Yes, it's better to buy a Mercedes built in the year 2000 or later. They had problems with transmission in some cars, but it was fixed starting with 2000 models.
ML320 is a good car, but it's an SUV, so it rides almost like a truck, not as a Mercedes sedan. If you need an SUV, then go for it. As for the price, I don't know if it's a good one. Go to autotrader.com and see what they are selling for.

Dont buy anything before 2000. Mercedes are really nice but if your only gunna speed 6000 dont buy it. Stick with used japanese cars.

Mercedes are good cars IF they are taken care of. Just make sure the owner has the maintenance records on the vehicle. Just remember that insurance and other repairs will be more costly.