swapping exhaust questions?

[DEVL-XR]

well today i got a letter in the mail stating that my car needs to go in for an exhaust sound test. i was spotted at shepp. at the springnats, on the Saturday at 11am on the main street of shepp. heading out to DECA.
its from the enviromental comminsioner (spelling!), so now i need to get it tested.
when i bought the car the guy said he thought it was only just over the limit, so im thinking i'll put my old standard exhaust on for the test, then swap it back after the test!!
so im wondering if its just a matter of unbolting and taking it off. i know theres rubbers it hangs on to as well so how do you take them off?
my exhaust is a 2.5" cat back with 1 muffler and a hotdog at the rear, thats all.
my standard exhaust sitting in the shed is a 2" with 2 mufflers in the middle and one at the back.
am i best swapping over the whole lot or is it possible to swap just 1 half of it? if so which half am i best swapping?
and if i just swap half will i need an adapter from 2" - 2.5"? this is why i am thinking its best to swap the whole lot??

sorry about all the questions! just want to find out as much as possible!!

cheers
Braden

ps. did anyone else get a notice?