Bit by the Wind-door pillar split

The wind blew my passenger door open further than it was supposed to go when my daughter got out. It split all the way across the Lower pillar just above the hinges mount. I looks like rust from the inner side is the culprit. My question is how to replace. Just cut the piece out and weld in a replacement. Is there anything special I need to do. Ill send a picture tomorrow when the rain stops.