Autobox Trouble

[uselessmechanic]

hi all
i have 2 e36 bmw's
the 1 i need help on is my 1993 320i auto
it has a gearbox fault
will not change into topgear of drive tries to but keeps kicking back out
i have tried speaking to my local main dealer and they arnt very helpfull
i am a trained mechanic so i really loathe the idea of paying someone else to look at my car
what i need help with is topping the gearbox level up im pretty sure this is the problem
this is the gearbox without the dipstick and according to the main dealer there should be a small alan-key plug on the side of the box to check and refill the box
however i cant find it
heard stories about these being sealed units etc but not sure about that
i have drained a small amount of fluid from the box and the problem has got worse hence my belief that refilling will resolve issue

having spoke to the techs at the main dealer they tell me they do nothing but replace the gearbox for new units anyway so they dont actually know anything about the box itself
im hoping 1 of you are far more incitefull

[mmclaren]

I dont know if this will help but when the car is in manual switch it will only use 3 gears, found this out last night dragging, it wouldnt shift into drive when the switch was on manual mode. So deep into the red lines i went before hitting the switch off and pressing the brake. I dont know if somehow that switch may be jammed into manual shift or wat.

Chances are this wont help but i tried :P