As Eric says, if you have a hydronic water heater/furnace combo, do not rely on just blowing the water system out with air. Use the water pump and a tube into a couple/three gallons of RV antifreeze to at least get the "pink stuff" antifreeze through a hot water faucet somewhere in the coach, if not through all faucets. Then you know the hydronics coil(s) is protected; a new unit costs many thousands. If you don't have hydronics in your '98, simply blowing out the water system may be adequate; it worked for me on our old Pace Arrow because I was very thorough, but isn't ideal. Don't forget to blow out or flow antifreeze to any outside shower faucet.
Also, just a couple other oft overlooked points:
if you have a washing machine, pour a cup or two of antifreeze in the tub and run a rinse cycle to protect the pump that lies at the bottom and is where water drains to and can freeze, breaking it. A half cup of RV antifreeze in each P trap should be adequate, and don't forget the shower drain - there's a P trap under there also.
If you have an ice maker, stand alone or in your freezer/fridge, you'll want to protect the solenoid behind the unit. Pump antifreeze through by manually cycling the ice maker, or drain and blowout the in and out tubes of the solenoid, and/or safely apply 110v voltage (others here can advise how to do this carefully, because I haven't yet) to the solenoid itself to open it to blow it out, leaving the tubes disconnected for the winter. It freezes easily and is only plastic - it will crack and leak next time you hook to or pump water. It's easily and affordably replaced, but why go through unnecessary hassle, esp. if you don't catch the out-of-sight leak right away.
Joel