I'll give this a shot, here.
If you're gonna tackle this, here's what you're looking at:
First, you'll need to drift out the mainspring housing pin, located near the bottom of the MSH. I use either a 1/16 or 3/32 punch for this. Probably gonna have to remove the grips to accomplish this. Once the pin is drifted out, the MSH can be removed from the frame by sliding it down the "guide slots" inside the frame. Once that's done, things get a little more complicated. Take a look at the MSH once its out of the frame and you'll notice there is a small pin near the top. That pin holds the mainspring, mainspring cap, and mainspring housing pin retainer in place, for all intents and purposes. To remove that small pin, you have to apply pressure to the mainspring cap in order to free up that pin. You can use a punch for this, but be careful as a compressed mainspring has plenty of energy and will go flying once that pin is removed if you're not careful
. Anyway, once you compress the mainspring by applying pressure to the cap, you can drift out the small pin. Once that small pin is drifted out, SLOWLY release pressure from the mainspring cap and then remove the mainspring cap, mainspring, and mainspring housing pin retainer from the MSH. At that point, you can install the new MSH/Mag Well into the frame and check the fit. Assuming it fits (and most mag wells won't fit flush, in my limited experience) without excessive friction or wobble, you can continue. To install the new MSH, you have to reinstall (in this order) the mainspring housing pin retainer, the mainspring, and the mainspring cap into the new MSH then apply pressure and reinstall that small pin that holds it all inside the MSH. Assuming you have no problems there, you can install the new MSH onto the frame and then secure the MSH in the frame by reinstalling the mainspring housing pin. When reinstalling the MSH, make darn sure that the sear spring is properly positioned in the frame, as the MSH does apply tension to the sear spring once installed.
Hope that made sense, but I bet that RC, Tuner, Fuff, Rogers, etc. can explain it a heck of a lot better......
In closing, remember that any issues that a magazine well may attempt to solve (specifically, the speed of magazine changes) can also be corrected through proper training....