how difficult would it be to turn my taco into a 4x4?

Till you have a wreck and you tell them they need to replace all of the 4x stuff that's now messed up.

 

Need the front diff, cv axle, spindles, bearings & hubs, driveshafts, fj manual case is easier to swap than tacoma, 4x4 transmission, add kit to engage front end, custom rear driveshaft because the axle flange is different, custom trans crossmember, exhaust on from 4x4 truck. It probably wouldn't be to hard if you have the tools skills and a donor truck.

 

http://bham.craigslist.org/pts/3914302538.html heres a donor truck in alabama