The part you linked to, # LC334785 does not have a speaker however, the Solera Power Awning Speaker Idler Head is, # LC342150 is available. We also have the Replacement Slip Ring Assembly, # LC330961 to replace the current slip ring assembly in your Solera Power Awning LED idler head. view full answer...
We can start with the over-under conversion kit since that is pretty simple. Since you have a 2-3/8" axle you will need the Dexter # K71-384-00. This will allow you to mount the leaf springs on top of the axle on your 2012 K-Z Spree.
Moving on to the brakes, I'm assuming with your 2-3/8" axle that you have 3,500 lb axles. Make sure to verify this information. Assuming that is the case, you will need the following:
-Electric Trailer Brake Kit - Self-Adjusting - 10" - Left and Right Hand... view full answer...
Feel free to email me back with the pictures you have but in general just a single roller like the # 295-000180 would be all that you'd need to level the one corner that is lower. I would recommend checking to make sure the tracks of your slide out aren't misaligned as that's a pretty common reason for sag. view full answer...