I have a 2000 dodge ram 1500 van and the heater blows out cold air only---along with this the engine revs up very high at idle. I feel these 2 problems are connected. Any advice as to what to check first

The Engine Coolant Temperature Sensor and the Idle Air Control Valve may be affected by the problem with the heating system. Using a scanner, see if your truck is throwing any codes. Try and identify and fix the heater problem. After checking for any codes, disconnect the negative. Battery terminal for 20 seconds and reset the computer, making it relearn everything all over. This may help idling and even transmission shift points.

I have a 2000 dodge ram 1500 van and the heater blows out cold air only---along with this the engine revs up very high at idle. I feel these 2 problems are connected. any advice as to what to check first
Understand I am not a mechanic, but first thing I'd do is check the quality of the coolant in the raditor, perhaps you have had a radiator leak in the past and tried to stop it by using something like "Stop LeaK" and this gummed up the radiator and possibly whatever lines might run by the heater.