About 30 minutes with the correct tools - just gets a bit messy as you'll no doubt get trans fluid all over yourself 30 minutes if the approximate time for mounting in the stock location; not relocating it to another place.
No need to bring it to a specialist workshop; just bring it to a normal one.
You'd also be advised (as one very wise person did to me before) to get a Oil Temp Gauge for the A/T; especially if you're going to track the car. You'd also be advised to fit the sender when you are putting this cooler in.
From memory; the DC kit comes with everything you'll need - you will need the following extras: 1) side cutters, 2) screw drivers, 3) socket set, 4) zip ties, line clamp tool x 2
Cheers
Stan