We had Gregorian Chant at our Mass last Sunday. It was so beautiful. Our priest brought in a couple of young men from Benedictine College to sing it for us. Their voices were amazing. I wish they were there every Sunday!
Grab a couple of others who would be foolish enough to try and start your own schola. If you break the selection into small pieces it is not as hard as you would think. The great thing about chant is that since it is monotonal you do not have to worry about harmony. This also has the advantage that you can have a complete choir with only three of four people singing the same notes.
It should also be remembered that it is written in a relative key. In other words just sing in a range that is comfortable for everyone. It is the interval between the notes that is important, not a perfect pitch. If you can sing do-re-me you can sing chant. Chant also lacks a strict timed beat as in modern music. Just allow the notes to flow around the words. (There is a theory of rhythm but it need not concern you.)
Your results may not be perfect but do not allow the perfect to be the enemy of the good. In many ways chant is more natural than modern music and in time you will get the hang of it. Since your priest has already shown an interest, if you showed interest and initiative I am sure that he would provide the resources you need.