What's the impact of a crystal's frequency stability, ESR and load capacitance on micro-controllers?
It would probably be better for you to choose a crystal oscillator rather than a crystal. You just buy it and it works, and is guaranteed to start and conform to stated specifications. 

If you are using a crystal then you need to consider drive power, load capacitance, accuracy as well as other things. In the datasheet they recommend you to refer to the crystal manufacturer for information. The crystal manufacturer will likely be similarly unhelpful and point you back to the IC maker. 

You should get the load capacitance correct. Refer to the formulas for calculating it, which I won't repeat here, it's not simply the stated load capacitance stated for the crystal, it's double that minus whatever capacitance is built into the chip or exists parasitically. 

If you exceed the maximum drive power you can cause early aging or even failure of the crystal. This is more of a potential issue with smaller SMT crystals which have maximum drive power of 100uW or less compared to mW for HC-49 style crystals. Lower ESR is better. Some crystal manufacturers recommend you measure typical drive power, which requires special FET probes. You can determine an upper limit to the drive power from the ESR, but that may be too constraining. Low frequency tuning fork crystals (like the typically 32.768kHz crystal which your chip can use for one of the oscillators) usually require a series resistor to limit the drive power. 

As to whether frequency drift and initial accuracy is a potential problem for you, only you know to what use you are putting the chip, so this is entirely for you to evaluate from a system point of view.