I'd like to trade my cross bike, which is too big, for a road, but don't know which o

[bikecanada]

Really? It's basically brand new though ( 4 months old). I thought they would trade for more

[Biciclista]

a lot of shops won't take used bikes at all; they have to be able to make a profit reselling it.
Hang in there; someone else will answer your other questions.