As mentioned above the cat back is just a replacement (wider & better flowing) exhaust that can be installed by itself.
A turbo back replaces the downpipe that is attached between the turbo and the cat back portion of the exhaust.
When changing the downpipe you change the flow of gases exiting the turbo so it is recommended to get a retune done to the
ECU, you will gain more power/torque from doing so but the cost of a tune is a fair bit to some people.
Tuners can be found in the
Perth Workshops thread.
This picture should help to visualise the differences between the two.
As for detailing, Adam from OCDetailing did my car a couple years back and I'm glad he did!