If it was me, I wouldn't want to chance welding into the tube and possible weaken it. I would bend what I could to as close to straight as possible and weld a 3/16 plate onto the existing plate staying away from the frame tubes with some drilled spot welding holes to keep everything held to each other. The 1/2 inch skid plate you will get will be strong enough so you just want to carry that impact zone through a bigger support area. I am not the best welder and my welder is crap so that's why I would personally never take the added risk to weaken the frame tube by welding into it. I would take it to a specialized welding shop to have it done if taking that approach.or I weld a couple tabs to the existing bent metal and try to pull it back into place and then either leave it and put the new skid plate on or also add something to strengthen it.