1992 Explorer 4x4

My uncle has a 92 Explorer 4x4 4.0 with the following tranny problems:
She won't go into reverse. She has abt, 160K miles on it.

(1) What do you guys think could be the problem?

(2) How long do these transmissions usually last?

(3) If the tranny is bad how much is the normal cost to rebuild.

(4) Do you know of a good/honest mechanic or shop in the Milwaukee area you would recommend for inspection &/or repairs?

Thanks in advance,

-TuType