Thanks to Chrisay's suggestion I opened mine up today and repaired successfully. The motor is in a sealed plastic case which can be fairly easiy split open by running a craft knife along the seam.
It's a poor design on Subaru's behalf. Motor sits at the bottom of the case where molten grease collects (and there is a LOT of it). Hopefully with all the excess cleaned out now I am good for another 6 years.
I wrote up a DIY: