If you can prepare your new drive and set it to be bootable, then copying the files is relative easy. AmigaOS doesn't lock system files like Windows so you can copy system files from your live system whilst it's running. If you copy the files then the partitions can be different sizes.
You can use the copy command with CLONE option to keep all the file attributes. I created a small script called Quikbackup which gives a simple GUI for this purpose
http://aminet.net/package/disk/bakup/QuickBackup. I created and used it when I had to swap out a failing mechanical drive for a Compact Flash.