Once you have re fitted your wheels you need to make sure that the rear mech end stops are correctly set. These are designed to stop the chain and R/mech going in to your wheel.
With the bike in a workstand or with someone else holding the backend of the bike off the ground. Whilst turning the pedals around manually push the rear mech body into the lowest gear. The mech should (with the force of your hand) push into bottom gear without the chain going over the top into the wheel.
If the chain goes over the cassette into the wheel during “adjustment check” immediately grab hold of the outside of the wheel to stop it from spinning. Re-place the chain onto the largest sprocket and adjust the lower adjustment screw clockwise until you feel resistance then stop. This is the screw hitting the shoulder of the r/mech stop and will prevent the mech from going into the spokes.
Once these checks have been performed, once again by manually spinning the pedals shift into the highest gear. If the chain will not drop into the smallest sprocket gentle turn the “high gear stop” screw anti clockwise half a turn and re check. Perform this until the chain drops into the smallest sprocket. Hope this helps. If you are not sure about anything give us a ring.