Have you done church work on piano before? Make sure you obtain the details of the position and what will be required of you, so you can make an appropriate decision. Find out if this is also a music director position. Are you required to direct choirs? Are you required to program music for the church? If so to what extent (hymns, anthems, special services, concerts, etc.)? Are you required to be in attendance certain times of the year such as Christmas and Easter? Keep in mind this may mean missing out on family gatherings which tend to occur at similar times. Are you required to attend committee meetings?
If the church has a piano, perhaps start with it. You can work organ into the mix as you gain more skills with the instrument.Regarding repertoire. Church music does require you go through large amounts of repertoire in short periods of time.
Another thing, start improvising if you do not already do so. This is an extremely useful skill in church music.
We introduced plain chant into a very low church congregation.
Only do it if you really need the money (i DO hope they pay you, right?). Still, its a good experience (for a short time), and it is some fun trying to push up the speed of all those singing old people