OP, you don't say how old, how many miles or what work you're having done to it, or the condition of the vehicle.
You should only be equally as concerned about a breakdown as you would with a car of similar age miles and condition.
Your class C is basically a 1 ton Chevy or Ford truck chassis and drivetrain. As reliable as any similar truck.
If your concern is due to it being old and in not so great mechanical shape, then I'd say it's a valid concern. If it's just becasue you haven't had a motorhome before but it's in good order, then I wouldn't be very worried. No more than if you feel having roadside service on your car is necessary.
To ease your mind, go drive it a bunch. It's 24' so you can drive it anywhere, which will probably help you become familiar with maneuvering it in traffic and tight areas. Also, putting some miles and hours on it will either reinforce it's reliability or potentially uncover items that need work.
Tell us about the rv and maybe you can get specific suggestions as to things that need attention due to age or miles or brand.