It's very easy - well within your capabilities to swap. I pioneered the change from MFT to Sync3 and couldn't be happier. Lots of units at the wreckers for you to steal one out of - nav or no nav it's a worthwhile swap. (
Link here for swap info)
Installing a sub was also a worthwhile adventure - I just went the cheap route with a 2 channel sub and tapped in to the rear speaker line with a line adapter and after turning the bass right off in the head unit, I couldn't be happier. Decent enough for me! The van spoils me but I listen to the exhaust a lot in the Fiesta so no complaints regarding the mediocre speakers.
Also, whenever I buy headunits and such, I'm buying Pioneer. Very happy with the longevity of the one in my 4Runner and the double camera unit in the van is pretty slick too. Most likely can get CarPlay in their new units.