Hi, I was advised to check that the roof goes up and down smoothly, I have heard that this can be a problem, although not experianced it myself yet (fingers & everything else crossed), as the micro switches can be a bit tempremental. But they are truely great fun cars, best car I have ever had.
I am sure others will be along with some other pointers soon.
As Lisa says, check the roof works correctly and smoothly.
Also, check the engine wiring loom to ensure that there's no oil in it from the cam position sensor. The easiest way to do this is to remove the cover at the front of the engine and pull the plug off the cam sensor connector. It's also worth checking at the pre-cat O2 sensor connector as the oil migrates all the way down to there as it's the lowest part of the loom.
lovely car and the roof is a piece of art but look out for rust especially around the rear boot release and check everything inside works like the seats and that includes manual seats as it was designed and built in mercs dark decade.