This is an easy road repair. Obtain seal. Someone can correct this number if incorrect for your bike, but I think it's 23-12-1-338-740.
Find a tree. Prop bike on right side against tree. Remove shifter lever. Remove old seal with screwdriver. Careful not to mar the bore. Press in new seal, just below flush on the casting. Replace lever. You won't lose much gear oil but you can top that off later.