A quick search says that the Kia Sorrento is rated to tow between 2000-5000 pounds depending on your particular options and equipment. That's a big range.
A 12' boat isn't very specific either. Worst case, a heavy 12' boat with a bigger motor and a good trailer could weigh more than 2000 lbs, but a lightweight rowing dinghy could weigh much less.
Would need more information to make useful suggestions.
In general, I've installed both Reese and U-haul hitches and they are typically easily bolted on with factory holes and provided bolts.
Wiring can be anywhere from extremely simple to complicated depending on your vehicle's accommodations (or lack there of) for wiring. On a Toyota I did, it had a plug by the spare tire that by ordering a special adapter, I could just plug stuff in and mount a trailer light plug. Most vehicles need a trailer adapter to be wired in and then the plug for it.