What size tire iron do I need & other questions...

I purchased a new Jayco Jay Flight 28BHS last autumn and it came with a spare tire mounted on the rear bumper. I luckily haven't needed it yet, but I know the day will come when I get a flat tire on the side of the highway. What my travel trailer didn't come with was a tire iron or jack. I need to know what size of tire iron I need for my lug nuts, which are 1/2-20. Is that a 13/16" tire iron?

On a side note I'm thinking of purchasing a "trailer-aid plus" instead of a jack. Does anyone have experience with it and have any thoughts?

http://www.amazon.com/Trailer-Aid-Plus-Tandem-Changing/dp/B001V8UKBY

Thank you for your input!