Radiator change

[grasmere59]

I'm looking at changing the rad on my 2003 110 exec,it's not that the one on the car is leaking but i've a new one in the garage and with the "summer" (ha ha) coming i thought it wouldn't hurt to change it as it's the original one on the car,what's with the bottom hose connection to the rad? Is there anything i should have to hand before i do the job? is there an "O" ring needed on the bottom connection?