3rd gen. factory cassette... difficult install?
 

I have 2003 ES on order right now (with the 6-disc in-dash) and I wanted
to install the cassette deck as well.

Would this be a difficult install or really easy (since the cassette and MD
player are both modular)?

I'd rather just get it cheaper from Mazdastuff.com rather than pay for
the high dealer's price and their install.

Two screws and it plugs right in.

why not get a nice aftermarket HU that plays both CDs and casettes?

Theft, interior good looks.

I've already had one car stereo stolen and my roommates' a couple
months ago. I will eventually swap out to better speakers and add an
Alpine amp with speaker level inputs. Maybe a Kenwood Woox sub.
That will sound plenty good for me then.

all you have to do is obtain the cassette deck....remove your deck from the dash...pop out the little rectangle between the volume and tuner knobs....just pushes in...and pop the cassette deck in....it PLUGS in to the head unit...and your ready to go.

Not to beat the horse, but it is very easy and designed to be modular so dealer can sell the parts for big $$ and then have mechanics who maybe outstanding car technicans but know zero about car audio be able to pop the unit and install the extras in ten minutes.
A true do it yourself job.
I am not using my stock deck right now, but I have traded around now so my has the 6 disk and the cassette in it for whenever I put it back in the car.