1998 Dodge Dakota Heater doesn't blow hot

I would try changing thermostats first. It could be a quick and cheap fix. If that doesn't do it, it could be plugged heater core and flushing may help. As far as the a/c, it may just be low on freon. You can buy a recharge kit at any parts store, but there are a couple of tests you should try first.

Not knowing what part of the wourld you're in or how cold it is, but what works good is disconnect the heater hoses from the engine(not the heater core) and use a regular garden hose. Or, you can use an air hose, blow it out, add some water to the hoses and blow it out again. You can do this several times, BUT, --you have to be careful with air so you don't blow up the heater core. On adding freon, if you buy a 134 recharge kit, it will come with instructions. Most important is to be sure you are on the correct hose for charging.