Threw my Rebel down the road the other day Minor damage for what it was, just lever replacements (and a ding in the tank that's gonna annoy me forever) - but I also tore up the casing at the top of throttle cable A. I've looked at changing it out but it seems like access to the throttle body end of the cable is quite awkward, even if I take the tank and seat off.
You will probably have to take the gas tank off (or at least unplug the fuel pump electrical connection and a couple of hoses to move it enough...NOTE: to fully remove tank you also have to relieve fuel line pressure before separating the quick-disconnect...see shop manual on that procedure) to see where to thread the throttle cables down along the frame. The lower cable ends are mounted on a bracket secured by two phillips screws...remove screws to move bracket into a workable position to unhook cables from wheel on throttle body shaft and from the bracket.
Get yourself a shop manual...there is information in the Tech/Maintenance section on how to obtain a FREE factory shop manual that you can download. Will be handy for procedure to depressurize and disconnect fuel line in the event you want to remove fuel tank completely from bike and how to adjust your new cables....plus for any future work you may do on your bike.