What's a reasonable price for a 2-car garage permit drawings & retaining wall designs (9ft high)?

Hello!

First time poster here.

My 2-car garage wall is being pushed in by the soil in the back (the house behind sits at a higher level -10ft higher). I guess my block garage wall is acting as the retaining wall, but over the years is starting to be pushed in. This is in Toronto (Etobicoke).

I was wondering a few things:

1. What's a fair price for designing the new back retaining wall and permit drawings for the garage.

2. What's the cost of a new 25'x20' garage. I'm thinking wood framing with aluminum siding.

3. Does the city allow me to just repair the back wall and keep everything for the garage.

Thanks!