1st, W5M312RRTE is a 4wd gearbox, if im not mistaken is taken out on RVR body.
Certain gears were hard to engage, i guess ur gear level MAYBE is not original
and ur question
1)yes 2wd gearbox is pricer than 4wd gearbox, coz 4wd gearbox easier find than 2wd
2)yes compare 312 4wd with 312 2wd...