Owner's manual's pretty good; would suggest a service manual, too: either a Clymer or a Kawasaki edition.
Couple of things about checking oil level (do it, early and often!): Bike should be held level when checking (not on sidestand), and . . . WAIT for the oil to drain into the sump after operation to check the level. The oil disappears from sight when the engine runs.
Some believe "doohickey" (idler shaft lever) upgrade is immediately, urgently, and mandatorily needed; I'd disagree on the time-criticality, with a new bike under warranty; and--while spring tension issues have surfaced, I know of no late-model (last seven years) doohickey component failures. But; your bike, your choice!
Welcome to KLRdom; your modifications depend largely upon your application; out-of-the-box, the bike's rather capable, IMHO.