The paper gasket kit is a couple-o-dollars. https://www.sjscycles.co.uk/search/?...gasket&geoc=DE

It's super easy to change. Use a torx bit to remove the gear select gearbox and then remove the 2 Philips "cross-tip" screws. The entire mechanism will basically fall off with both paper gaskets readily accessible. Replace the gaskets and retorque the screws to about 2nm not more than 3nm. (About hand tight with thumb and forefinger on the small end of an Allen wrench)

Have you tried to tighten any thing, or did you see a leak and immediately jump to outside service help?