I'm going to write from experience. I'm sure there will be many that will feel that my info is wrong, but this is what I did, not out of knowledge but out of panic.
I will combine both leaks.
Back seem slit 5:30am. Removed all LR into 2 Rubber maid Garbage cans.
Removed all coral into shallow rubber maid container.
Removed 5 fish (one Tang) into 10G tank
Inverts went into Coral tank
Sand into garbage pail
New tank arrived in two weeks. That two weeks with a tang, 3 Chromis and a Blenny in a 10G. Amolock was used but Ammonia levels were through the roof the entire time. (AmoLock makes Ammonia less deadly to fish but will not effect the readings from test kits)
New tank arrived. Wet tested for a couple of hours
added new water (About 20G) brought up to temp and added salt.
Added sand Ran power heads and Skinner plus some filter floss.
Next Day added LR and water from LR buckets. Drained some of the New water out.
Next Day added Coral and Fish. Zero Losses.
I must admit I got lucky. The fish I had during both mishaps I still have today. 9 Months later. All coral I had then I also have today. One Shrimp was lost several days after
As you could expect I don't sleep very well anymore. Always one ear on the tank.
I hope this helps some what. The only advise I can offer is to try and slow down. I was always in a panic trying to get the poor fish out of that dam 10G. If you have the time to do things right or make improvements to your system this is the best time to do it.
Good Luck
Jason