The seal is a rubber o-ring, which with age becomes hard; that’s
Probably the source of the leak.

The housing is a twist lock fit; remove it by depressing the small
Tap on the housing and turning CCW then pull up. The tricky part
is disconnecting the cable end from the rod in the case. First Disconnect
the inner cable (not the outer) from the throttle linkage on the engine,
This would allow free play in the cable at the case end.

At the case pull the cable housing up, with a needle nose pliers grab and hold
the steel rod, you should be able too side the inner cable end off of the rod.

Reverse the procedure for installation.