Firstly… Stop… Breathe…Calm Down 
Ok, well done on getting the set. Its always the most exciting thing for a bedroom DJ moving on to a Club.
But make sure your not too overexcited, even though you’ve said yourself your not a veteran acting as professional as you can be goes a long long way.
Promoters are generally too busy or not bothered about communicating with Djs anyway so dont feel like you are being ignored and they probably know nothing about the PA system anyway… If your using a S4 then you will probably only need a RCA cable to plug into the mixer at the club… normally the club will have some cdjs and a mixer already set up into the PA system, so just plug into a spare channel and your good to go. It does really help to go have a look before the gig, maybe one quite night jsut so you can see the booth and the space you will have. Remmeber your only one of potentialy a few djs so you have to think bout how easy it will be to pack up while the others are playing.
You said this is the biggest club in your area so id be suprised if they didnt have the PA already connected, heck there might even be a sound engineer to help you set up. Turn up atleast a hour before the night kicks off… that way you can make sure your plugged in and ready to go and also introduce yourself to the club owner and the promoters, maybe even a soundcheck.
On to set lists:
Everyone has their personal opinions about pre planned sets, there isnt a good or bad in either. I think its great to have a idea of what songs you would like to play during your set, but i wouldnt neccesarily have the whole hour’s set planned out. You never know what might happen, what if the crowd reacts different to how you had planned, or the promoters are impressed and ask you to stay on for a extra half hour (it does happen) and you panic because youve already played your ‘planned set’
Id create a playlist and pick the tunes you want to play, then from now untill the gig just keep mixing them in different ways and orders so your not planning but your used to all the songs and are confindent of mixing in between all of them. Also remember you are the warm up Dj, dont go in playin absolute bangin tracks, the best of the best, because your job is to get the dancefloor nice and warm ready for the headline dj. That dosent mean you cant play any big songs, but be wary. This has been coverd on other threads before.
Lastly i remember how nerve racking it can be but Djing is supposed to be fun right? Enjoy yourself and relax, get some friends to come with you nice and early so you have that comfort. Its ok to have a beer before your set but dont get Drunk!!! And most importantly Have FUN.
I hope this helps even a little matey… Let us know how you get one!!
Best of Luck