Switch out the X1 Oscillator on a RPI 2/3

This is a not a very fruitful idea, for several reasons.

The clock circuit on an embedded device like the PI is not designed for accuracy or stability, there are more elements than the XO that will affect jitter and drift.

1. Stability and drift in the Phase-Locked Loop (PLL) inside the Broadcom CPU which generates the core clock
2. Temperature Drift in XO resonance circuit
3. Temeperature drift in the latching/clocking threshold detection circuits.
4. etc. etc.

Additionally, Any hand rework, even with good equipment, runs the risk of wiping out any improvement from a better spec'd oscillator. They are very sensitive parts.

The improvement in temperature stability switching to a different XO in the same package is marginal, you are buying better tolerance and matching characteristics that reduce clock drift and temperature dependence for the device class, but physically speaking all crystals will expand/contract with temperature changes and all will experience clock drift, very hard to compensate for this.

In the end its unnecessary, if you want to run an NTP node it will work regardless, if you want to function as a (local) time standard you will need to interface external equipment, Like a GPS, thermally stable clock, cesium clock, etc...

However, If you want to experiment with stabilizing the on-board oscillator this I would suggest and alternative approach

OCXO

Clock references in precise equipment are usually in a constant temperature oven, and require some time to stabilize. These "ovens" provide a constant temperature (not necessarily HOT), usually controlled by a Peltier Element

These devices are known as Oven Controlled Crystal Oscillator (OCXO). Unfortunately they require a significant change to the circuitry and are not drop in replacements.

They Look like This:

To experiment, you could replicate some of the stability of an OCXO by putting a Thermo-Electric Cooler (TEC aka Peltier Element) to keep the XO and the broadcom CPU at a constant temperature.

In other words, eliminate the temperature issue by keeping the Raspberry PI at constant temperature.

1. You'll need one with exactly the same circuit characteristics as the stock XO.

2. If you're skilled with a hot-air rework station, and have all the right tools and equipment, it's not too hard. It's virtually impossible if you don't, though.

3. Likely not. NTP is designed to work around variable system clocks through network consensus, so changing the XO won't give you much. Using a GPS's PPS signal effectively gives you a GPS/Multi-GNSS Disciplined Oscillator, so as long as you have skyview, you've got atomic clock accuracy even without a network. If you don't have skyview or network, it wouldn't be impossible to piece something together based on a used rubidium frequency standard — but even the cheapest of those have fearsome power requirements and are far from plug-and-play.