How difficult is it to set up a laptop that can run either MS Windows or Linux? Can it be done by a non computer professional/geek?
Yes.
Method 1. Download Linux Mint Cinnamon iso and either burn it to a dvd or download iso2usb and create a bootable usb stick. Boot the laptop using this iso. Once running, you can try Linux without affecting your hard drive, and if you like it, click on the install icon and answer the questions. You need sufficient free disk space (at least 60gb ) to assign to linux. Downside, you can only run either MS or Linux at any given time. If you decide not to continue with Linux, in MS fdisk, delete the linux partition and expand the MS partition.
Method 2. Download and install Oracle VirtualBox. Use it to install a Linux VM from the .iso file you dowloaded for method 1. VirtualBox will ask the same questions as method 1. Upside, both MS and Linux are available at the same time. But, you will need at least 8gb of memory and sufficient disk space. If you don't like it, delete the folder containing the linux vm.