For the price, not a bad deal at all.
1) Swapping suspension systems is common, don't be concerned.
2) You should feel the locker in the front quite easily when turning as it engages and dis-engages.
3) The Super 35 kit comes in various ways depending on the brand, lock-rite, Detroit, and ARB.
a) Pulling the differential cover will reveal which locker is installed, if it's an ARB you'll see the airline entering the diff without pulling the cover, as well as the interior switch.
b) Most of these kits come with 30 spline axles, however some do have 27 spline to reduce cost.
Call and ask to open it up and see to be sure. Bring a supply of gear oil with you.