Transmission question

K i have a 92 brougham, never had a problem at all out of it...the other day i got into it, put it in reverse and heard a pop, then all of a sudden i have no reverse and no drive, runs great otherwise. Now the car did set up for about a year before i bought it, so maybe do you think i could change the tranny fluid and filter and that is the problem, I had a shop look at it and they say i need a new transmission (i am a woman tho, so they may think i am stupid too), but we have never had a single problem...no missing, no slippage, struggle, anything....any advice would be greatly appreciated.

No fluid change will correct this, something failed internally in the trans, assuming the drivshaft did not come apart.

thanks for the positive comeback...I would be able to visually check the driveshaft right, or would that be an internal deal too....you mean the u joint right?