It's possible that it's the starter, but it's also possible that it's a weak battery, the battery cable from the battery to the starter, or a loose connection. The older ones are know to have internal corrosion problems with the cables. If you have access to a multimeter, it's easy to test. Just check for resistance from the battery down to the starter. If it's more than a couple of ohms (say, more than 20 ohms), it's a bad cable.
First thing I'd do is check the connections to the battery and starter to make absolutely sure the connections are good. Then check the voltage from the battery. It's possible you have enough juice to run accessories, but not to start
Changing a starter isn't difficult. Just takes a socket set. If I remember correctly, the X has 3 bolts holding the starter on and 2 wires. You should be able to do it by putting the driver's side up on a ramp or jackstands. If you end up changing out your starter, make sure you disconnect the cable from the battery first so you don't short something out.