Sorry to hear about your problem Topline,
There is a Hopmog member who converted his +8 from manual to auto, and he might be a useful source of information. However this was the "old school" type slush box , not one of the modern dual clutch types. He wrote an article in Miscellany a few years ago , that might be searchable (?) Sorry no idea on cost.
If you want a modern auto with all the bells and whistles (as fitted to most tin tops nowadays) then I think your only choice is to sell/trade your current car for one of the new MMC offering (Plus Four or Plus Six).
I suspect that installing an auto in your current car would be the cheaper option , but would it be the better one? I think you need to drive the new Plus Four auto and ask yourself if you like it , if yes I think you have an answer (albeit requiring extra funds)
