Find an organist who can be bribed with cookies to make you a few arrangements that show all the changes that the bass line would imply and stand by to practice a lot. for instance

C G C   G   C F   C    G   C    F    G    C
wel come hap py morn ing age to age shall say

is a pretty good example from the easter section of the Episcopal hymnal. The hymn melodies are usually moderately simple, but the harmonies are often majestic. That kind of chord line can often be accomplished with just a change of bass note or 2 note chord sequences -not as daunting as it might look.