Manual HVAC controls removal (linked from Toronto Mazda 3, lots of dead pics but the important parts are there.)
The conventional wisdom, and has been proven numerous times, is the stock Passenger Motor Mount (PMM) does not last more than 60,000 miles. Smptoms vary, but include knocking noises (from the metal portions of the mount banging together), vibration, and wheel hop on wet pavement or uneven surfaces. If you are past this, replace it regardless of whether it looks broken or not. ROCA Passenger Motor Mounts (and other unconfirmed) are solid rubber rather than oil filled, and may last longer. Polyurethane PMM's probably will never wear out, but will almost certainly vibrate the cabin more.
The stock struts and shocks ALMOST NEVER last longer than 100,000 miles, typically they start to lose some damping by 60-80K. At 100K, they are either dead or significantly diminished. There are no exceptions.
The factory thermostat typically sticks open around 80-100,000 miles. This will cause the engine to warm up slowly, poor heater performance, and a check engine light (verify with a code reader). DO NOT get any aftermarket thermostat, as many were reported to have failed very prematurely. Go straight to the dealership for this part, and enjoy another 100K or use.
I personally recommend the owner of ANY 2.3L engine'd first gen car convert the cartridge oil filter (filter housing with a black cap on it, takes cardboard filters) convert to "can" oil filters (conventional discarded oi lfilters). This can be done using Mazda parts, will use a 2.0's conventional filter, and there are no downsides. Several owners have had the plastic cap crack, and the resulting oil leak lead to spun rod bearings when the oil level falls too low. Here's my source for the conversion, though the parts can be had at any dealership and multiple retailers. Before you order this kit, if purchasing a used 2.3 car, verify that the conversion hasn't already been done as it's not an uncommon first modification.
For automatic cars and Mazdaspeed3's. Maintains the factory oil cooler. Failure to keep this cooler has dire consequences even for stock cars, it's there for a reason.
For manual equipped NON-MAZDASPEED cars. No oil cooler, no extra fittings.