1.  Just take either some parts and time or some ingenuity and more time.  Not a big deal. 

2.  Transmission wise no problem.  Shifter quadrant in the cab doesn't really lend itself to this if I remember right, however.  Wonder if there was every a shuttle shift used with this tranmission?   I'm betting the transmission is capable but there may be no controls availible to do it.  Might be able to build your own.  Would definately take into consideration advice from someone who actually knows these tranmissions well, but the 8 and 15 spd Deeres are fully capable of reverser operation if you can rig the linkages to make it happen.  8 spd Deere's had left hand reverser control availible as early as the 60's and most of the parts are in the parts system.  

3.  Have to keep the front and rear tires circumstances proportional unless you want to change gears in the front end.  May not even be any alternative ratios availible.