All fluids on the bike have been replaced. No worries there!
Good man
The top box is compatible with brake lights yea, might look into it in the future. Would look awesome but I'm not sure how it will wire up as I want the top box to be easily put on and taken off.
Relatively easy if you buy the wiring kit, it's plug and play really with a plug you disconnect when taking your box off.
Or the other route is do it yourself, buy led's to fit, connect to a plug (plenty of waterproof ones on fleebay) and that's it. Only difference between the two versions is price
Here's my extra brake light I put on under my topbox bracket as I sometimes take my box off and this way it's always on the bike regardless of topbox being on or off and no wires to disconnect either, but I didn't have space to put led's without cutting the box somehow.