thats nothing to repair by looks of it, sierras have a bonus of engine crossmember making inner wing/chassis legs rigid and they crease right next to the engine crossmember if they are hard hit, chop the front bodywork crossmember/frontpannel off and you will probebly find its fine when you offer new one up, iff not i`d just portapower the legs out and keep measuring untill perfect, sounds rough maby but i`m used to building bumped rallycars in a hurry for the next stage LOL

Seriously, seems easy repair tho.