Yes new gasket its under 20 bucks. All the perimeter bolts are reused. The little sump screen bolts 3 per screen is what triumph says to replace.pictured below dots next to them
Myself like stated above clean everything with brake clean because it evaporates. Then apply medium grade thread locker. You can get a pen of it at like advance auto parts or any other local auto parts store. Doesn't have to be loctite brand. Just a medium grade blue as for crush washers I have a sack somewhere but haven't ever changed one yet. I change oil every 5000 miles and reuse the washers. You need to figure out why its leaking. Impact with a shift or possible damage, someone already have it off ? Thats why cleaning and unspecting is important. And double check the filter that us a mess under there maybe spray ?