Well lets see, take a cold chisel to the aluminum tongue where attaches to the chassis surrounding the pin. Giving it a few "digum smacks" strike the aluminum several times until you see it break around the pin, remove the broken debris, remove the tongue from the door. Take a die grinder or a dremel tool and attach a cutoff wheel, cut the pin in half. Now that the pin is cut you will find that it is much easier to extract the two pieces from the anchor points on the chassis. This approach will maintain the painted finish on the chassis side as well as reduce the frustrations of dealing with that tightly fitted pin. Remeber to purchase a new pin for the reassmebly process.

As far installing the replacement check strap there are a couple schools of thought, you choose the one that you are most comfortable with. 1) You can trim the triangular nub on the opposite end of the pin joint of the aluminum strap so as to ease the insertion of this strap from the “outside of the door frame” OR 2) Remove the springs from the holding assembly and install the complete assembly (strap and holder) inside the door frame. Once fitted to the door reattach the springs by using an awl (CAUTION: You will be installing the springs some what blind, you may be unable to see the anchor points clearly and/or directly. You can/will damage your extremities if you are not careful!!!) I encourage practicing this method a few times with the strap assembly mounted in a vise so you can have a clear idea whether it will/will not work for you.

Unless you understand all the adjustments which affect window sealing I strongly discourage disassembling anything to do with the window since it can/will make your life challenging.

PS: Let me know if either of these methods work for you