There are many bag choices I had an 07 Classic and upgraded it:
Bags: Quite a few are available and it opens up your options with quick disconnect bag mounts. Easy Brackets, Viking Bag, National Cycle. Then choose from a host of bags. I sold my Triumph leather bags, got some mounts and then selected a heavy duty synthetic leather bags. Viking, Leatherlyke....Viking universal bags are about $200 and very sturdy so you don't need bag guards.
Windscreen: The stock Triumph windscreen was worthless. Saying you want a taller Triumph windshield suggests you have a standard with mounts. Recommend Clearview. They come in different sizes/widths and will run about $200 for smoked.
-Engine guards. I chose Rivco because at the time the Triumph ones were very flimsy. I have Triumphs on my 09 Touring and they seem fairly stout, plus they are 1 1/4 so many highway pegs brands are available.
-Get yourself a factory shop/service manual either in PDF or hard copy and it will contain everything you need to know about fluids. I buy motorcycle synthetic oil at the local auto shops. Digital copies are about $11 on ebay:
Triumph Rocket III Classic Touring Service Workshop Repair Shop Manual 3 Factory | eBay
Pic of my Classic with the aftermarket bags and Clearview windscreen in gray tint.
Welcome to the forum.