I pull a 14" single bottom plow with my
B7610, so you should have no problem pulling one with a
B7800. Of course if you are opening new ground it will pull harder. But I have little doubt the
B7800 will pull it even when opening new ground in sod.
Getting a 3 point plow to "track" properly takes some time, trial and error and often times experience. The first furrow is always the most difficult. It is hard to explain how to set the 3 point arms, upper link and the plow itself (assuming it even has the option, some do, some don't) over the internet. If you have access to an experienced farmer that is willing to help you set the plow and tractor up, that may be your best bet.
I spent many years using 4 bottom plows to turn soil as I grew up on a farm. It takes time and patience, but you should be able to cut a nice furrow after some trial and error. You just don't hook up a 3 pt plow and go to work. Just keep trying different settings. If you are plowing new sod, it will take some patience.
Good luck