That was one of the challenges of my transfer. The 46 had been in place for 5 years, so I had rock encrusted together with coral growth. I had to take the rock out in large chunks. Everything did ok when I moved everything to the 90, but the rock was challenging again with placement in a larger tank. We added more base rock before adding the sand/water and kind of built everything back up over the base rock.
Here is a picture pre-transfer. I had to take off that top section with the monticaps in a huge chunk. Incidentally, this tank was set up in 2008 and there is Baby Clown, who still lives in the 90 today!
The biggest calamity was my prized brain coral in the lower right. I had had that piece for at least 4 years and somehow during the transfer, it split in half. My ICU nurse daughter-in-law proceeded to do "brain surgery" with superglue. It always helps to have an ICU nurse handy.
I hope yours goes well. The transfer day was one of my most stressful days ever!!