A little more progress on this situation has happened, It's not what I wanted to find but hey it's found now

Drained off a little bit of the ATF out of the gearbox into a glass jar, It's black and it stinks burned really bad! Not just dark brown, I mean black with a brown tinge, it's so bad you can barely even see light through it

I'm guessing that this means that something has burned out in the transmission and i'm unsure whether just a fluid change for this would be appropriate given the expense of a new filter, the sump gaskets and the new oil

I guess it would explain a lot with the bad gear changes and missed gears along with the limp mode being present ... Question is, what to do about it now ?
I know AR25 boxes are cheap as chips, but I'm wary of buying a used one as I don't have anything concrete to say how it was on the previous car other than the buyers word (and we all know what some people are like)! For me there are few options A] Sell the car with a dead gearbox and get nothing for it! B] Source a used AR25 transmission and battle to change it on my own! or C] Take the car over the bridge and cut my losses as I don't want to break it for spares due to the lack of space and storage with having my brothers Princess in the garage atm!
I haven't the cash to pay a garage to do the work for me so that's well out of the question, the damn thing has already bled me dry and I don't even have any reserves left

.... So yeah pretty stumped now really
