In this situation, I advice you start practicing the organ playing with the right techniques and methods in private but for public performance you could limit yourself for the time being with hymns only.
And here's how to approach the hymn playing so that you would get still satisfactory results but at your level of accomplishment (which is rudimentary):
Play only 2 most important parts of the hymn setting - soprano (being the melody) and the bass (being the foundation of harmony). Take soprano with the right hand and the bass - with the left hand. Add a solid principal chorus registration with mixtures (even with 16' as a foundation).
This way you can learn to sight-read hymns for church service or to practice them diligently so that you will be ready to play 6 or 8 hymns during your liturgy in a week. But of course since you are really a beginner at the organ, you will need a lot of practice so plan accordingly and practice adequately at your church also.
This technique of playing only the outer parts without the pedals doesn't mean you should stop practicing real organ pieces, exercises, improvisation, and music theory training which help you progress even further at your own pace.
It's just a shortcut for you to jump right into the church service playing, show immediate results so that your congregation could sing together with your playing and practice diligently on the side the regular things.
[HT to Angela]