2007 Yaris hatch - thinking TRD

[Type-Y]

I've had my 2007 Yaris hatch for a little over 2 years now. I got it as our 2nd car (my wife is the main user of our primary, a 2016 Subaru Forester - love the Forester, we're on our 2nd one). When looking for a 2nd car I wanted something simple, reliable and small for easier city parking. Something I didn't have to worry about getting dinged or scratched (It came with some of these and some new ones were added, but I don't care). I got it from the original owner with 48,000 miles on the odometer (sitting at about 59,000 as of this post). I call it the toaster, because to me it was (and is) an appliance, just a small, reliable, well designed car to get around the city.

I love the car. It's cleverly designed and it's truly roomy inside; it feels like a bigger car when you're sitting in it, which I can't say about the Smart or Fiat 500, which I also considered. I've sat in the back seat as a passenger and it is comfortable back there (I think it has more leg room than our previous Forester which was a 2007). It has a great amount of storage space (not to mention all the cool, various storage compartments), with the back seat down it has surprised people with how much it can fit. Overall, it's a great city car and I could easily live with it as our primary vehicle.

The other thing I wasn't expecting is that this slow (but pretty peppy, from 0-25 at least ) little car is actually fun to drive. It handles well, with an almost go-cart feel zipping around town. That brings me to the post title. I'd like to enhance that go-cart like feel. I've been researching sport springs and the rear sway bar and based on what I've read, TRD is my best choice. My questions are:

1. What's a good place to order these parts from?
2. How much can I expect to pay for installation?
3. How much harsher will the ride be?
4. Can I keep my stock struts/shocks for now?