Just like maintaining a car, or cooking, some tasks are more difficult than others.
If you can follow a recipe then most of the suggestions here will be within your reach. However o give you an idea I will include a simple rating system with each post, plus and an estimate of how long each task will take.
Should be something attainable by your Grandmother, as long as she knows how to use the mouse and the keyboard.
If you use a PC in an office then this should easily be within your reach.
Not too difficult, but it will involve some knowledge of how PCs work. If you know how to install software, navigate around the computer using Windows Explorer (or similar) and how to copy files from one directory to another then you should be fine.
Starting to get a little more challenging. For this level you probably need to know how to install drivers on the machine, or make changes to the system using control panel.
About as hard as I would put out there for novices. You will need to know how to install drivers, and may need to change system settings at a low level (registry editing). Most users are capable of this, but many will find it intimidating. For this level a system backup immediately prior to starting any work is definitely recommended.