NWheelspin & water_power20 are spot on. It is a straight forward, fairly simple install, especially if you have access to ramps/lift & the right tools. But if you don't, I called a few local shops (NE WI), and was quoted around $80. And the Curt Hitch (114112) is actually on sale for $125 right now on Amazon (I know Amazon says this hitch does not fit the GTI, but this is the exact one I purchased & installed. Read the reviews too, many GTI owners state it fits). Check out the links below!

Install: https://youtu.be/R31n0SMiOLg

Hitch: https://www.amazon.com/dp/B0133WU3K8/ref=cm_sw_r_u_apa_fabc_AVD7TB6J8279PN20F8VR