No idea who makes the Scion radios. So I cant say if corolla can use the scion radios... something to look into... But just because they are both for toyota, doesnt mean that they will be the same height.
I noticed that some of our newer radios are 2DIN high but much wider. actually, the radio is not bigger, but the trimplate is.
If you get an aftermarket radio from one of the larger retailers, they will usually install it for "free". Actually, its not free, but that what they say.
If you order on-line, someplaces will include all the mounting hardware (crutchfield.com)
good luck.
and let us see some pics when you are done with the install.
tdk