Well, buy a bushing tool. Clean the frame and bushing threads before trying to install them. Use
blue loctite, and be careful not to cross thread them. Nothing really involved about installing them, just be careful and don't force it. You should be able to screw them in all the way with your fingers, and just torque them with the tool. The bushing tool is really just for breaking them free and torquing them down.
I like to use the little o-rings to keep my grip screws secured rather than loctiting the screws, but as long as you properly loctite the bushings it shouldn't matter if you loctite the grip screws too since the screws should break free quicker than the bushings. I have had one or two grip bushings unscrew from the frame before I could break the grip screw loose of the bushing, but that was on a factory gun that apparently didn't secure the grip bushings in any way other than torquing them down.
As to why the grips didn't fit, well, are they slim grips on normal bushings? If not, I don't know what to tell you, unless one of the parts is just plain out of spec. Normal grips use normal bushings, slim grips use low profile or slim bushings. Don't mix and match. You could probably use normal grips over slim bushings in a pinch but that's a quick road to cracked grips, IMO.
Oh, and you'll need the proper length screws if you're using slim grips too. I highly recommend slotted screws. It's a lot easier to find a screwdriver or screwdriver like tool than an allen key or, heaven forbid, a torx bit when your grip screws loosen up at the range. The 10-8 grip screws--normal length only but you could grind them down I guess, I probably would--are expensive but you really can use a 45 case rim to screw them in securely, which is purely awesome.
I've butchered at least 20 grip bushings (I have owned and worked on 15 1911s, it's not just because I suck), and that's even using a bushing tool. You need to keep a lot of pressure on the bushing to unscrew it cleanly without deforming the edges of the slot. Put the frame in a vise and use a good bushing tool and you won't have problems. Take a shortcut and try to remove the bushing with the frame in your lap (like I usually do), and you might go through a lot of them. They're soft steel. Using a screwdriver instead of a bushing tool is the quickest way to wreck a grip bushing, of course. Save that for emergency repair.
I believe the thread pitches are standard, but I'm just going by the fact that I've never heard/seen differently. I keep my all spare grip bushings in a bag and pull them out as needed, regardless of manufacturer or what gun I'm putting them on. They seem pretty standard to me. I usually buy Ed Brown parts and I'm happy with the quality, but I'm sure there are plenty of good bushing makers around (or most of the bushings out there are single source, just rebranded...).
Were they really staked? There's no need to stake screwed in bushings, that's kind of the point of threading the frame holes to begin with. They might have really, really torqued them down which is normal, but if they were truly staked this is the first I've heard of anyone doing so, for whatever that's worth. I'm skeptical that it's possible to stake a threaded bushing without causing obvious problems from the start.
My last bit of advice is buy two sets of bushings, and an extra set of grips screws. It's easy to botch the bushings even with the right tools if you tinker with your guns a lot, and it really sucks when you're down one screw or bushing and your whole gun is pretty much deadlined because of it. There's a reason guys who shoot 1911s a lot keep a tackle box full of spare parts
.