Succeeded in pressing new bearings into my PowerTap SL+ yesterday.
Here's the procedure I followed:
* Pulled both axle end caps off by hand
* Pulled freehub body off by hand with cassette still attached
* Gently tapped axle on the drive side with a rubber mallet to push out the non-drive side bearing
* Removed axle
* Turned axle around and used it to gently tap out the drive side bearing
* There are no electronics exposed inside the axle cavity, just a magnet taped to the axle
* Used bearing press to push in new 6902 bearing on the drive side
* Slid axle in the from non-drive side
* Mount freehub so bearing press would push against the cassette lockring rather than the drive side bearing
* Used bearing press to push in new 6802 bearing on the non-drive side (both axle and non-drive bearing push home)
* Reinstall axle end caps
Note, all surfaces were cleaned, degreased then lightly greased before pressing.
In the end the drive side bearing was fine, it was the non-drive side bearing that was barely turning at all. I popped the seal off the old bearing and there was more dirt than grease inside.