replaced throttle position sensor with unit from mercedes part distributor, had intermittent problem starting, then, soon, car will not start, also, code reads misfire on #1 cylinder, how would I check this?

 

Did you check the wire connection to plugs on cylinder one.Left hand drive that would be 1st cylinder passenger side front of engine.

 

I had the same problem with my wifes 2001 ML320. The solution was changing the Fuel Pump and the Spark Plugs, Yes, sounds extrange but was the solution. Before taking the ML to my local MB shop I change the throttle position sensor (TPS) with no luck. In this case the ECU send signal to the fuel pump, TPS, Injectors, etc. If the fuel pump sends not enogh gas the hole system crash and the engine wont start or hesitate, the OBDII scanner will give you TPS problem because is the one who works with the Throttle body who send oxigen and gas to the engine, obiously the fuel pump is working but incorrectly.
I hope this information will help you, good luck...