The 28/42 combo you're considering would be a really low gear ratio. I know you said you pull a big dog in a trailer, but 0.66 is still pretty extreme unless you're climbing some crazy steep hills - like mountain bike climbing. The 26/34 on the Roam 2 Disc gives you a 0.76, which should be plenty sufficient for riding roads and rail trails. And like hokiefyd said, the geometry of your Escape isn't designed for a suspension fork. If you drop your selling price to $200 and add that to the $450 you planned to put into the upgrades, you'd have more than enough to buy a brand new Roam 2 Disc.