http://m.summitracing.com/parts/SUM-7882300

I'm wondering how much would a mechanic charge me to install this?

 

Ask them. Some of the instructions say 8 hours (rough country), but it'll depend on rusty bolts too.
But 3 guys at my son's workplace threw one into his 92 in 3 hours - which comes out to 9 hours I guess.
Shops usually charge 80 to 120 an hour.
Plus you'll need an alignment.