Thanks everyone, still thinking about it, my mechanic friend has all the facilities (it's a big workshop with 4 ramps, mot testing etc etc) it's the garage I used to run. After speaking to him properly today, he reckons someone has already tried the fluid change, so looks like it'll be a box change, he's a good mate and won't charge me for the labour. The bloke who's got the v6 is considering my offer and getting back to us on Wednesday, so that gives us a couple of days to find prices for a secondhand box, cheapest I've found so far was a 4x4 breakers at £400 (but they always charge more than private sellers, so we'll see, let me know anyone sees one for sale please