Hello Kevin, welcome and I think you will enjoy the car, it's a lot of fun.
I would think twice about lowering it, the car's already been lowered a fair amount from the non-ST Fiesta. The Ford engineers put a lot of careful thought and effort into the development of the suspension, I wouldn't change it just for the sake of change. Here's a fun YouTube video, a conversation with one of the engineers who designed the car, I have found it very interesting.
View: https://www.youtube.com/watch?v=M7YKS9CnpJg
The other things sound good, lighter wheels are a great upgrade. A tune for a little extra power is always nice, an exhaust doesn't really add any power, so just get one if you like the sound better. I have Sync 3 and it's a good system, so that's a nice thing to have. Enjoy.