OK, I have a brand new iMac (not the machine I am using here.) How do I get it running and copy/transfer all my files from my old (2007) iMac?

If you have a TimeMachine backup of your old Mac (if not, you can still make one on an external disk), using Migration Assistant is an easy and safe way to do this

https://support.apple.com/en-euro/HT204350

If I remember correctly, when you start up the new Mac, just follow the instructions. I believe that you will also be asked if you have data to transfer from an old machine. You will be directed to the Migration Assistant app and told to do the same on the other Mac. One 'sends' and one 'receives' data. Do not rely on wifi to do the transfer as it's too much data and it may get corrupted. Rather, you should connect the two machines together with a USB cable. You may also use an ethernet cable if that is what you have. The transfer could take around an hour, if I remember correctly. All of your preferences, etc will be transferred.

Your apps such as Microsoft office will also be transferred, but you may have to re-register some of them to activate them in the new computer. If any of those apps are old 32 bit programs, they will no longer function in the new computer and you will either have to update them, when possible, or purchase an upgrade. Some people recommend deleting the apps from the old computer (before the transfer) and doing new installs in the new computer. I'm sure other people will also have some good information to add. Good luck and enjoy the new Mac.