Hi Tricia,
This is a very common problem. First, DO NOT use heat except as a last resort.
Soak the connection point in lots of penetrant/lubricant. WD40 will work, but there are other better brands out there as well. After giving it a little time to think about its crimes, try to gently work the lever back and forth. Keep in mind that the weakest link is the plastic knuckle above the pivot point. If you want to exert a little more leverage than you think the plastic knuckle can bear, use a locking pliers on the lever. If gentle working isn't working, you have a full-blown stuck lever.
You need to drive out the roll pin that holds the vertical lever in the horizontal shaft. It's best to use a roll-pin punch, but most people don't own a roll-pin punch. A dead blow punch will work in a pinch. Soak it with the penetrant again and give it a little more time to think on crimes committed, then drive out the roll pin. I'll warn you - it's a pain. The pin is gonna take some grunt to get out of there. After the roll pin is out, you'll need to drive out the lever. Get the biggest dead blow punch you have a drive it out. This is where you MAY (but I hope not) need a little heat. Make sure you aim the heat away from the transmission. There's a seal behind this lever that WILL leak if you cook it. Replacing the seal requires a little time in the transmission. As you try to drive out the lever, use that locking pliers to work it back and forth again.
After you drive out the lever, take a drill and the appropriate sized bit and clean out the hole in which the lever sits. Then emory cloth the lever and give it a nice coat of anti-sieze. Put it all back together the way you took it apart and enjoy!
Bill in WI