No, if your mag pouches and holsters are fitted for a 9/40 they will not properly hold a 45. There are differences in the overall length and the length of the trigger guard area. It's less noticeable in my Duty Pistol rig, but the snap will not fasten, even though the rest seems to fit. With my Raven Concealment holster it's much more noticeable. 45 mags are noticeably longer than 9/40's there's just no way those pouches will work. The grip however feels identical to the 9/40, it's really amazing how they did that given what Glock did with the 21.
ETA: Once you smooth the trigger out you'll love the 45, smooth accurate and very, very manageable.