You have a great starting point but I want to offer some ideas and thoughts.
For mounting windows etc, cut a oversized hole in the metal, using sheet metal screws and fender washers, fasten a piece of plywood to cover the hole from the inside with a bead of caulking to seal it to the metal and simply mount the window in the plywood. This will seal and secure the opening and allow you to fir inward for insulating or inside wall covering. A piece of sill seal or backer rod and some caulking will fill any corrigations or convulusions in the metal wall. Same idea works for man door openings, coverable wire air vents for the summer, outside access laying boxes, run door openings,etc (protects you and the birds from the sharp edges)
Using a skil saw to cut metal works well and it's very fast but it's definately noisy, can use dull wood blade if you run the blade backwards but wear a face shield, wear ear muffs, wear heavy gloves, and wear long sleeves due to metal shards and sparks.
The major problem with a metal building is condensation, chickens put out a LOT of moisture, both breathing and in their poo. This creates a huge problem keeping them warm when it's cold out and they're damp and being dripped on.
You didn't fill in where you're at but if your cold weather is not too bad (above 0), your birds should be fine without insulation, especially if they have a covered sunporch or run to go out on in, in the winter and soak up some sunshine during the day and there are enough to huddle at night, might hang a heatlamp if you're concerned on a real cold night. If you use foamboard, you should cover it, chickens love to peck at it, it doesn't hurt them, it's just fun for them.
Hope this helps and hope you have fun with your project and your birds