My rig is also on the lower end side of towing (3500 for travel trailers and 4500 for boats, I think due to a low tongue weight limit), and I have no real complaints about it's capabilities. My 177 is at 3200lbs on the scales fully loaded, and the 179 is a little heavier by the sticker, so you're pushing it a little closer.
I would agree that some sort of sway control is in order, but I went with one of the $35 curt sway control units. The difference it made was absolutely night and day. I've got a couple thousand miles on it with the sway control now, and it tracks like it's on rails under all conditions, high wind, big downhill grades, whatever. Prior I was limited to 55 - 60 mph to control sway and would have to modulate the trailer brake down hills. Not good.
As far as towing with an under powered vehicle, the biggest problem I have is poor gas mileage and a relatively small fuel tank, my rig had crappy mileage to start with though. The only time I've been worried about engine power was Tioga pass going into Yosemite. It's a brute of a hill, going up and coming down. Turn the AC off for big long pulls.
Get a full size spare tire, I picked up a matching wheel from a junk yard, and it fit fine in the factory location. You probably aren't wired for a 7 way connector, so when you pull wire, pull a 8-10 gauge power cable from the battery so you have enough capacity to run the fridge on 12v and keep the batteries topped off. My wiring kit came with a 10 gauge power wire and it's enough for the fridge and battery charge, if I'd known a bigger power feed mattered at the time I would have bumped it up to an 8 when I pulled it to be safe. The Tekonsha P3 brake controller has been great for me.
Minimum you need the factory oil cooler that comes with the tow package,you should be able to buy it separately from the other parts, ideally probably have an after market unit added in addition to that equipped with a thermostat on it so the oil still warms up from cold in a reasonable time. That one is on my wish list...