I have just finished a pictorial history on the West Baden Springs
Hotel.  I use several pieces of music as background to certain eras. 
Two pieces of music I use are Tennessee Ernie Ford - Nearer My God and
Chuck Berry - School Days.  Both songs (lyrics) are public domain, but
I'm not sure if it's legal to use about the first minute of each
recorded song on my DVD without permission.  I would like to sell the
DVD eventually.  I doubt that I'll ever recoup the cost of putting it
together (hard costs/not labor), so I will never "profit" from it. 
What is the answer?  Do I need to find two other pieces of music to
use, or is it safe?

to do this you would need to get in contact with the publisher of the
music. due to the fact that these are old songs, and it won't be a
large publications, a publisher would probably just tell you to do
whatever until it is in a more serious distribution (i.e. 10,000
copies).