I would say that if you are taking the parts off because they are damaged from the accident then just take them off any way you can. If you were removing the clip to do some work then putting the same clip back on then maybe it would be easier to do in one piece, but this isn't the case. Repros don't fit the best so when you put it back together just attatch the fenders without the inners while you are lining everything back up. Once the fenders are lined up then install the inners. I find it easier to play around with the fenders while the inners are out. The inners go on no problem with the fenders on anyway. Thats the way I do it but everybody has their own way that they find to be easy for themselves. Once you do it you will have your own way that you do it that you find easy.
87 K5 Siverado, 68 SS 396 Camaro