how do i check and where do i pour???

i have a 2002 isuzu rodeo w/73k miles.it started leaking transmission fluid so its been @ the dealer for 3wks.my question is where is the dip stick and where do you pour the fluid?the service tech. said the one of the seals had a cover and it cracked :?: i have no idea how true that is but for some the reason there was no oil on the dipstick when my husband tried to check my oil the same day the trans. started leaking.could someone please tell me what could be going on???also one more thing when i start to come to a stop (not everytime) but the whole front end vibrates like crazy,so bad that i almost ran out in front of a car because i couldn't stop.been told it was the abs??what do you think??
thanks
april