Get one of those 100 gallon rubbermaid agriculture tanks to keep your livestock in during the transition. I use one for makeup water for water changes - always handy to have around. Someone was selling one recently on MAAST.
Setting up another tank is exciting and hair pulling at the same time. I purchased a used tank when I upgraded and it still took several weeks to get the plumbing and electrical worked out. Thought it would never end.
Instead of replacing the front glass and if you had enough space, your current tank would make a kick ***** sump.
My Reef System: 215g Brick 72x24x29 Dual Overflows | 4x 250w MH | 4x IceCap 39w T5 w/ Actinics | MSX-250 Skimmer | 1/3hp Chiller | 16w UV | Aquacontroller 3 | Lunar Sim | AquaSurf |Tunze Wavebox | 2x Tunze Stream 6101 | MRC Dual Nano Calcium Reactor | GEO Kalk Reactor | Pan World 150PS Pump | Phosban & Carbon Reactors