New to you TT and no manuals? Check this out:
Forest River RV Online Owners Manuals
Your bearings may be fine but I'd want to ascertain that. You'll need to pull the dust covers for the hubs and observe the quality and quantity of grease at the outer bearing. You'll also want to determine that the bearings have been tightened properly. Grasp the top of the tires and push/pull it in/out perpendicular to the axle. There should be very little relative movement and the wheel should rotate freely.
Suspect your TT has seen very little use. Many are purchased on a whim and sit for one or two years until the owner/s decide it's not for them.
I believe your slide is an electrically driven Schwintek. No reservoir for that.