Da'lan makes good quality hitches for Euro cars (that's what HMS is selling in the link you provided. I don't have experience with that exact hitch, but I've seen some of their other hitches and they are very well-built.
As for the wiring, don't make it harder than it needs to be. Use a standard "taillight converter" to tap into the taillight wiring, use those little scotch-lok connectors so you won't have to cut/splice the wiring. Then just get a flat 4 trailer connector for the car and you're there!!! (assuming the trailer you're hauling has a flat 4 connector...if not, just get whatever matches.)
Trailer wiring supplies like this are readily available- WalMart or your local chain auto parts place should have what you need.
Bret.