I did do this with a T50. I will simply agree that it is a bugger of a job whether you leave it in the car or pull it out (I ended up doing both - don't ask).
If you don't swap the worm gear (the 11 or 10 tooth gear) then you speedo will read incorrectly AND you run the risk of wearing out the driven gear. That risk in reality is not high unless you leave for a long time. I safely ran mine for 6 months before correcting the gears.