DME recommendations

Let me start by admitting my ignorance about DME's.
In my plane I have to KX-170Bs, one indicator has GS.
I also have an ADF.
I have no DME, and I've never used one.
I've started studying for my instrument written test.
I've noticed that a large number of approaches would either be more
difficult or not possible without one.
So, I've been researching getting one.
I don't need anything fancy, so I've been looking at older ones.

Here's my question...
Some DMEs seem to have an indicator, and then a separate receiver box, like
the ARC 800 DME.
Others I've seen just seem to be an in-panel job, like the Narco DME 190 or
the King KN62A.
I've seen some on Ebay, and wanted to make sure that the Narco 190/ King
KN62A don't require an additional recieving unit, like the ARC 800.
That is, if I were to purchase a yellow-tagged Narco 190 (and tray and
connectors), would that be all I need? Antenna?

Thanks,

Adam
N7966L
Beech Super III