If you get a NM 9mm cylinder,, it will USUALLY drop right in. I always suggest a person measure the frame window and get the measurements of a cylinder before the purchase. Next,, a proper check for cylinder alignment is always in order.
It's best, IMHO, to get a cylinder that is a couple of thou longer than your existing cylinder so it can be "fitted". Ruger's "generic" parts are usually quite similar in size but getting one a bit short can be a bad move and is not recommended unless one has access to some proper tools with which one can "shim" the cylinder so it fits properly. Chamber to bore alignment may or may not be satisfactory.
Bottom Line? Send the gun to the Factory and have the job done right!