It depends on how good your reading is, and how comfortable you are with reading what is basically the left-hand part of the piano score, plus whatever chords which might (or might not) be annotated in the score. From what I've seen, most of the tunes of the genre you are talking about, have the chords named above the vocal line (some even show the the chord-shapes there for guitar also…). So, you can use the left hand (lower clef of the piano-part, plus the chord names/symbols, plus you have the vocal line you can also refer to…
Like I said, it
really pays to be able to read…
I've had gigs which were just piano, double-bass, and drums, and was very tentative at the beginning, but the piano-player was really good, and helped me along.
One tip I learned is to pay very close attention to the conductor/director/pianist, especially at the rehearsals - what usually happens is that the rehearsals are maximised for covering the maximum amount of material in the allotted time, so it is very important to be right on top of the ball. There's often lots of skipping around (i.e. the pieces or sections are reheased out of order), and often, the rest of the band will only be brought in for the last 2 or 3 rehearsals (all the chorus/dancers/soloists will have been doing their rehearsals with just the piano, so they are already further along the learning curve than you). You might also find that the arrangements have been altered, omitted, changed, so again it's important to be right on top of what's going on.
I'm sorry if I'm pointing out all the potential problems, but quite honestly there is
NOTHING, absolutely
NOTHING, like the adrenalin rush which comes when at the end of a number, the audience is applauding and cheering…
YOU!
(Sorry if it's long-winded… )
(…nah,
not really…

)
Good Luck -
- Wil
PS - A couple of tips: photocopy the score; mark-up the bass-part or lines/chords which you will use, with a high-lighter (makes it much easier to follow especially if you're working from a multi-line score. Use a sturdy music stand - plus (most important) get a stand-light (I always take my own) - there's nothing worse than trying to read a part in almost total darkness…