Newbie needs help with springs and shocks

[xray scatter]

I am new to this forum and new to car modification. I apologize in advance if my questions seem stupid. I just purchased a Stock 2008 3 door LB. I was happy with the look and performance of my new car until I discovered this website. Now, there are so many mods I want to do!!!! Unfortunately, I can't do them all at once.. So, I have decided that the first thing I want to do is lower my ride. I have a few questions. I appreciate any help.

1. I am interested in the TRD lowering springs. The parts guy at my local Toyota dealership said that I have to replace the shocks and the springs. Why can't I keep the stock shocks and just replace the springs?

2. The price for the TRD shocks($500) and TRD springs($239). Is that fair?

3. Will this mod stiffen my ride and make it a harsher ride?

4. Will my MPG decrease, increase, or stay the same?

5. Can I use my stock rims/wheel covers with this lowering modification?