The closest Catholic church to Andover is in Rumford, 25 miles from Andover. The trail does not get any closer to Rumford for you to hitch in.
I operate the Pine Ellis hiker lodge in Andover, and would be very happy to take you to Mass--as long as I'm available which I usually am, especially with a couple day's notice.
Please e-mail me directly if I can be of further help, or can find information for you.
There is a Congregational church in town which welcomes hikers, if you do choose to consider another denomination.
Good luck and I admire your dedication to your faith.
Ilene at Pine Ellis, Andover, Maine
web: www.pineellis.com
email: [email protected]