Does the motor/gearbox assembly look like this?

If so, and only two wires come out of it connecting to the rest of your RV, then it's an electrically reversible permanent magnet motor.
If that's what it is, you can
1. Disconnect coach's House Battery. Take a photo of the connections or draw a diagram first. Helps if you tape all the wires going to Positive in one bundle and all going to Negative in another bundle.
2. Unplug or disconnect those two motor wires. Use jumper wires or a portable start pack and apply power to the two leads from an external 12VDC source. Motor should run and move Slide one way, Open or Close. Switch those external power wires and Motor should move Slide the other way.
Pictures aren't hard to post, but if you have digital pix you can't post, send me a Private Message with your email ID. I'll reply then you can email me the pix and I'll try to get them posted.
Anything to get you out camping!