I just took out the factory stereo from my 1990 honda civic and would
like to put a CD player in.

The connector from the car to the factory stereo is ISO (I guess?).
The stereo didn't have any wires leading coming out of it. It had a
female port on the rear right where two black rectangular connectors
from the car plugged in, plus what I assume was the connection from
the aerial on the other side.

Now - what kind of stereo should I get? Are all stereos nowadays set
up so that the car just 'plugs in' the back? Or am I going to need
some kind of adapter? There are only two speakers in the car (left
and right) so I just want to pop something cheap in - I don't spend
that much time in the car (however I don't own any cassettes so a CD
player would be nice). I know I could take the car in to Halfwit's
and have a spotty teenager do this, but I'd kind of like to do it on
my own.

Thanks in advance for any help.