No, I don't work for Golden Motor, I am a Golden Motor customer who helps with the running of this forum on a voluntary basis.
I have never needed to change the bearings on any of my Magic Pies, but there were some useful pictures of a bearing change on an MPII
(with external controller) in
this post.
Unlike the MPII in the above link, the MP5 is has one large and one small bearing, and you may need to remove the cooling fan/brake disc mount assembly to facilitate removal of the large bearing from the side cover if the bearing comes away with the side cover.
I don't think the controller needs to be removed from its housing, as the centre of the large bearing should fit off over the outside of it.
If the side cover with the large bearing pulls off leaving the bearing stuck behind on the controller housing, you may have to remove the other side cover to allow the bearing to be gently knocked off the housing using a small parallel punch on the inner bearing race by tapping evenly all around the bearing. So it might be better to tackle the large bearing first, just in case you need to have both covers off at the same time.
I would try and replace one bearing at a time after removing one side cover at a time, leaving the stator assembly safely inside the wheel.
Before removing the side covers, place a mark
(piece of tape etc.) in line with the tyre valve to ensure the cover is refitted in the same position. Then remove the 9 bolts around the outside of it. Use a block of wood to protect the end of the axle on the opposite side and then give the block of wood a nice big tap with a large hammer
(or wooden/rubber mallet) until the side cover separates from the motor ring.
Just to clarify the above, to remove the
left hand side cover, you tap the end of the axle on the
right hand side
(and vice versa).
Once the side cover joint has been loosened, it should be possible to gently wiggle/twist the side cover and bearing all the way off. A squirt of WD40 etc. may help.
Warming up the aluminium side covers with a hairdryer should expand them slightly making it easier to remove the bearings, but you will need to use a pair of suitable gloves to protect your hands. You will probably need a hammer and a suitable drift to carefully knock the bearings out
(unless you have access to a suitable bearing puller kit or the bearings are a loose fit).
There should be no need to remove the freewheel from the side cover as they can both be removed as a single unit.
With the cover removed from the axle, you should be able to drift the bearing out using a suitable punch inserted through the centre of the freewheel onto the bearing's inner race. Keep tapping it evenly around the inner race until the bearing comes out completely.
When fitting the new bearings, try to avoid tapping on the inner race, as any pressure required to fit them into the housing should only be applied to the outer race. The old bearing can be placed against the new one to help drift it into place by tapping evenly around the outer race until the new bearing is full seated into its housing.
I would place the outer end of the side cover
(or freewheel) onto a flat piece of wood to prevent if from becoming damaged during the bearing fitting operation.
The side covers are originally sealed around the edge with silicone sealant, but I just wipe a thin layer of vaseline petroleum jelly on the mating surfaces to seal the joint
and prevent corrosion, and it also makes it much easier to take apart again in the future.
Alan 
