Yes, I had to order a new grease cap through the dealership. I hadn't replaced the wheel cover yet, those are over $80 new, and I haven't found a used one yet.
The wheel cover isn't sealed, so I'd worry about that last. Just because you're new to working on your 100 doesn't mean you can't learn. Repacking wheel bearings is a great DIY project that isn't terribly difficult and it's a fantastic way to gain some basic knowledge and get your gloved hands dirty. YouTube and this forum can be very helpful. The inside of that dustcap is a good indicator that water got in there.
@cruiseroutfit sells complete wheel bearing kits at www.cruiseroutfitters.com