its just up there on the side of the house... i have cable and never took
down
the antenna... can i just plug the receiver into the wall jack or will i
do
serious damage?

Depending on the quality of the TV antenna it may be better than you think.
On some antennas the elements are just straight wires, but on some antennas
they are wires that are bent back over themselves. You can unbend those
wires and make the elements twice as long as they were.