Installing Alpine CDM-s620 and 99 radio/headunit in 90 wagon

I currently have an AM/FM casette in my 1990 Honda Civic Wagon 2WD. I
just purchased a radio/headunit and alpine cd changer from a 1999
honda civic and am wondering how I would go about installing it?

The Alpine unit connects to the radio with an 8 pin M-Bus connector.
The radio/head unit from the 1999 Civic has two peculiarities:

i) instead of an 8-pin circular connector for the CD Changer, there is
a DIN 14-pin rectangular connector. Where can I find this adapter to
wire the headunit to the changer?

ii) the radio is stock from a '99 Civic so it does not have any wires
sticking out. Also, the 1990 wagon has a 16 pin connector for the
radio, but the 99 civic has a 20 pin connector. I suppose I would need
to get both a female 16 pin to enter into the vehicle, and a male 20
pin to enter into the radio?

I'm thinking I need the following to do an install:
i) M-BUS 8-pin circular to DIN 14-pin rectangular (from changer to
radio)
ii) female 16 pin harness (from car to radio)
iii) male 20 pin harness (from radio to car)

Am I on the right track? Any other ideas on this? Where could I find
these parts for cheap?

Thanks!