Oh definitely don't trash it.
I haven't built a stepper controller for my magloop yet but I probably will at some point. Right now I just use a simple DC motor drive with limit switches:http://n3ox.net/files/magloopnew_lg.jpg
It's pretty easy to use band noise to get the tuning "about right" this way.
If you want to get started building a stepper controller with "memorized" or "commanded" capacitor positions, you can look at what I did build a stepper controller for:http://n3ox.net/projects/stepperswitch/
What you need is probably closer to another project I built, this one for the lab. It's a little "antenna rotator" designed to point an ultrasound transducer for flow measurements in different directions:http://n3ox.net/files/US_rotator.jpg
This uses a normal four coil unipolar stepper and a (really expensive) worm gear drive. The controller is also an Arduino with exactly the same MOSFET circuits as my other switch.
rotator is available here:http://n3ox.net/files/US_rotator_v_1_3.pde
This one is probably more up the alley of a variable capacitor drive. It has a serial interface that can be accessed using Hyperterminal and accepts inputs in the form of 0-290 degrees in 1 degree steps (could be much smaller actually) and moves the switch accordingly. It uses a 35:1 worm gear reduction ... but I had to machine the housing for it, so it's not a very good home project. But spur gears are a bit easier to use (you'll see that careful drilling was good enough on my antenna switch to engage those gears sufficiently).
So those might be some starting points for a controller for your loop. If you want it to tune to low SWR, that can be done too but is harder. I've seen at least one full-autotune ham loop homebrew project but can't find it right now.
Gears are available from places like Small Parts:http://www.smallparts.com
and Stock Drive Productshttps://sdp-si.com/eStore/
And probably more. You'll have to do some research to figure out the right pitch and size to get a drop in replacement but acetal ones are pretty cheap.
I've had good luck using Lego for medium torque loads, too.