I would say that the wifi range extender/repeater is the simplest way to go for the OP.

By far, the best thing you can do is get a good high gain antenna for whatever equipment you decide to use for a repeater. A good antenna will help with both reception and transmission whereas any power hacks will only help transmission and will do nothing for receiver sensitivity ... resulting in no benefit in most situations.

I just stumbled upon this site that had a lot of good info and some good equipment for sale that might be useful for assembling something to do the trick:
http://radiolabs.com/products/wireless/wireless.html

It even has packages of antenna/amp/wrieless cards for use on trailers/RVs/transport trucks that might be useful to you.

The money lost by damaging yout 770 while hardware hacking it could buy a pretty sweet range extender.