Power seat not working properly

Okay, the fact that it still can tilt says that the power to the seat is good as all the functions use the same power and ground. Your issue could be the switch or a failed motor. The seat motor operates using simple reverse polarity 12 volt power to move. Testing isn't difficult but can be a bit frustrating if the seat stopped in a position that makes access to the drive motors hard. If you can reach under the seat and find the motor connection for the f/r motor (it is a 2 pin connector with a light green wire with a dark green stripe and a light green wire with a white stripe that is the connector. All you need to test it would be a test light. Connect the test light to the two wires and activate the switch. If it lights up when you move the switch the motor is the problem, if it doesn't light up it's the switch.
Replacing the switch isn't real hard, you first gently pry off the control knobs, then remove the screws that hold the trim panel to the seat. Then you pull the cushion out to access the connector and remove it, then remove the screws that retain the switch.
If you couldn't reach the motor connector to test there you can test the motor right at the switch connector. For that you will need two short jumper wires. If you look into the connector it should look like the second image. To test the motor from here you would put one end of one jumper into the #1 position, that is ground, the other jumper goes into position #5, that is power. Now take the opposite ends and just touch them to the connections in #3 and #6, with them in one direction the motor should move, now if you reverse them the motor should move the opposite direction. If that works then the motor is good and the switch is faulty, if the motor doesn't move then the motor is bad.
75% of the time it will be the switch. If testing shows it's the motor, the repair isn't hard, but due to the age of the van finding the parts may be. Replacement of the motor would require the seat be removed, then the motor assembly is removed from the seat and the replacement bolted into place. There are also position sensors on the seat if you have the memory seat option that can fail. If one of those failed the seat will not move with the memory button but should still move with the switch so those are likely not the problem.