It sounds like your shift indicator cable is broken
its number 2 in the pic above ,,,,the other end of it goes to the shifter lever ,,, usaly it brakes by the shift lever and then your indicator is off ----the part is about $30 ----
in the pic above ,,this is the other end by the shifter that brakes,,, number 10 ....
if you need more info on this just , ask , we can go back and forth on this page
Is this something my husband can do - he is mechanical but not a pro?
yes he should be able to do it ----I charge $160 to install this thing ,,, so it he takes his time he can save you some money ----he does not any weird tools or anything ,,, and if he has any problems, just have him drop me a line on this page and I will give him a hand