What needs to be done?

1) Yes, loctite everything. Even if it is not directly attached to the motor, the vibes will still travel all over the bike. Maybe not so much with a 4 stroke, but better safe than sorry. Loctite blue, which is meant to be removable with hand tools. If you use loctite red, I think you need a propane torch and an impact wrench to get the suckers loose.

2) Fenders, definitely. Lights, up to you. Rack, depends on the construction of the rack.

Yes, definitely grease the bearings in the wheels, bottom bracket (where the pedals go through the frame) and in the steering head tube. There are a ton of good videos on youtube that go through the process. As far as grease, I think a lot of the guys just use automotive bearing grease? I have a can of Silkolene Pro-RG2 that I got yeeeeears ago when repacking my motorcycle bearings that I will never run out of, lol, so I just used that.

I don't think the type of grease you use is that important. Just keep the bearings greased.
You can keep the fenders if you have reinforced, tubular fender struts. There are some posts about that on this site.
I would slime your tires. A lot of members hate the slime and prefer tire liners, like Tuffy's.
I wouldn't replace serviceable tires.

This is just my personal preference but i use synthetic grease. Temperature doesn't affect it as bad as ordinary grease.