Xerun 2250Kv - Bearing refresh, need help

[immarcescibile]

I own a fantastic Xerun 2250Kv sensorless motor on my rally-cross Mugen MBX6. I have recently checked for the bearings' health and it seems that they need to be replaced.

1) I don't know the exact measures of the front bearing and the inner bearing,
please do you know it?
2) In addition, is it possible to install two ceramic bearings instead of the
traditional ones? Any pros and cons?
3) Finally, is it simple to change the bearings or is there any tip that I
should know before proceeding??

Please try to give me as many instructions as you can, thanks in advance, bye.