450es wrong oil, slipping

in 08 when i got atv, i didnt know muck[and still dont] about atv’s. jaso was not in the booklets i got, so i used equivalent as i understood it. owners manual did say GN4, just not motorcycle oil for wet clutch oil. 1,200 miles when i got it, now over 5,000. found out too late Pennzoil 10 w 40 is not the right equivalent, though some say it should work. Tonight i had a slip moment that was bad, and i am thinking wet clutch replacement is due, so to speak.
How much for parts, and if i got to pay labor, is that going to cost? i could get something used to carry me over, for a while, an then sell it. horses need water more than i can fix something right away. old an decrapidated, i am, unless it is just crapidated. sometimes you can get something for 4 or 5 hundred that will carry over for a few years, then get a few bucks back, when your done. i guess i like my 2000es too much and want to keep it. first atv, been through the ringer a couple a times or more than once on it, it still made it an so did i. it’s got heart. //Ed