Tom-
Almost certainly your new Mac will have much more storage than the machine that's being replaced, so no need to erase (delete) anything.
If you get it at the Apple store, they should set it up completely for you. I've been upgrading for so long, I just use Migration Assistant, piece of cake. Since my current Mac has been in service for six years and is up to date O/S wise, you may have a long time with a new one.
If you have a current Time Machine® backup, just take that into the store. Otherwise, the setup will require you taking your old machine in.
Almost certainly your new Mac will have much more storage than the machine that's being replaced, so no need to erase (delete) anything.
If you get it at the Apple store, they should set it up completely for you. I've been upgrading for so long, I just use Migration Assistant, piece of cake. Since my current Mac has been in service for six years and is up to date O/S wise, you may have a long time with a new one.
If you have a current Time Machine® backup, just take that into the store. Otherwise, the setup will require you taking your old machine in.