Don't be daunted, it's not that hard to do and don't be swayed by the big brands - as long as it's rated to the ADRs as a block of steel to pull your shtuff. I bought a TAG / Mikano, service was good, one day order to pickup for the MQ GLS. < $150 should be a reasonable install price if you decide to have it done.
Decided to install myself, wiring is a splice in so no extra harnesses - instructions w/wiring photos here http://bit.ly/2oAqZnK
Best o luck mate,