1993 e 280 auto transmission

[gomike]

My 1993 e 280 was not driven for about six months and when started again reverse would not work unless revved and then only on a flat surface. Also got some oil appears to be coming from front of box. Changed the oil only draining from sump and when first engaged reverse worked again until the oil heated up. Used top of range Nullon syntetic oil.
As it appears to be an oil problem I am proposing to drain and change the oil again but realise need to get the oil out of converter as well. Help please to make sure I do all possible before spending a fortune

 

[brigadier]

If you had a leak did you find where it's coming from. Also not good to mix different types of oil in gearbox. Always change with the same oil as you can't change it all without specialist equipment.