Can only agree with everyone else here - the nut is probably fine, intonation will change.
A little trick I used when I changed mine was to "copy" the saddle positions and heights one at a time. Since the B saddle (5th string) was now becoming the E, I repositioned it as close as possible to where the existing E saddle (4th string) was, then did the same with the 4th string, 3rd, etc. Of course, the C string was entirely new and had to be adjusted on its own. Due to different (overall and individual) string tension, you may need to adjust the truss rod, which will affect where you put the saddle height - but you should be somewhere in the ballpark.