Instrument cluster, Security and CD question for 01 Civic

Just purchased a low mileage 2001 Civic 5 speed for daughter near
graduating. Car did not have owner manual or service manual, but I spoke
with previous owner and verified regular service at her Honda dealership.
Also received positive report from an independent Honda garage at
pre-purchase inspection.

Car has manual locks and manual windows, no remote lock.

Driver and passenger windows have stickers "Immobilizer Anti Theft System"
with an icon of a padlock over the engine, and the rear seat windows both
have stickers "Vehicle Equipped with Traceable Identification Codes" and an
No-Theft icon. I don't know if these stickers are from factory, dealer, or
aftermarket. I don't see any immobilizer system, so it may have been
removed, or is so transparent that I don't see it.

The radio is the base am/fm/cassette, with a CD button, but no CD player or
changer.

This is our family's first Honda, so I don't have any expertise with this
model. I've ordered an owner's manual, and watching ebay auctions for a
good price on the expensive Dealer Service Manual. After these arrive, I
should have a little more knowledge (sometimes a good thing, sometimes a
dangerous thing .

Questions:
1. Is the immobilizer a factory feature, a dealer option, or aftermarket?
2. What security add-ons do you recommend (remember, this car does not have
keyless entry, just plain old manual locks)? If you have specific
brand/product name and where to buy, please include, and whether it needs
professional install or not. Since this car is in the top 3 most popular
theft targets, it will make sense for me to protect it as much as possible.
3. Does it make better sense to buy a used Honda CD player that fits in the
pocket right below the radio, or just completely remove the Honda radio and
replace it with a standard sized radio/CD player. I'm not looking for a
super sound system, just the easiest to install with basically decent
ability, but daughter has to have a CD player. We are not very fond of the
mega CD cartridge gadgets that usually are mounted in the trunk.
4. I believe this is a DX model, since it is no frills. The instrument
cluster has a 5 inch speedometer/odometer gauge, and a small temp gauge and
small fuel gauge, both bunched inside the 5 inch gauge outline just left of
the speedo gauge. Both of the far left and far right 2 inch gauge outlines
are empty. No tachometer or other gauge. Can I pull an instrument cluster
from another junked Honda that includes a tach and install on this '01
Civic? Does this Civic have the wire leads/plug to drive the tach, or will
I need to run new wiring? What other models/years are interchangeable?

Thanks in advance for any and all recommendations and answers.

Proud Dad