Auto help needed

[edroders]

ok, so the story goes. I have a S2 Fairmont Ghia and a few weeks back i noticed the gearbox slipped, it only happened the once and the fluid was cold, so i put it off. then it happened again, and i thought i've got a big drive coming up so i'll top up the fluid before i go, so i put it off for another week or so. not loang after this i noticed a whining coming from the box that sounded like a supercharger, but no slipping so didn't think too much of it, i figured that a fluid top up would fix it. so the day before the big drive and i top the fluid up untill it dripped out the filler hole and then started the car and ran through the gears leaving it in each gear for 30 seconds or so with the break on so i could bring the revs up a bit, then checked the level, all seemed good.

then the day of the drive and i nearly didn't make it up the hills, the gearbox was slipping worse than ever, and it has gotten worse since. i had to drive it a few K's the other day and it couldn't go beyond 35kph for the slipping... is the gearbox FUBAR or will a flush, new fluid and a band tightening fix it?