The 8 GB flash drive will be real helpful. I see three possible strategies depending on how adventurous you feel
Plan 1 - To backup your data to the flash drive and then burn the data to a CD or DVD for posterity and to free up the flash drive. I would do this on a weekly or biweekly basis. We can work through what directories you will want to backup in detail if you like.
Plan 2 - a little more adventurous
- do Plan 1
- Use a program called Clonzilla to make an image or picture of your hard drive and store it on the flash drive
- burn the image from the flash drive to a DVD
- this will allow you to restore to the state of your PC as it is TODAY - newer data must be backed up as it grows
- this method will not work when you drive gets filled with more and more data and becomes too big to fit on the flash drive
Plan 3 - Do Plan 1 and Plan 2 (just in case - we will be getting a bit more adventurous)
- Use a program called Gparted Live to divide the hard drive into a couple of "partitions" or areas.
- Linux, your programs, configurations and preferences will be stored on a small partition
- the rest of the disk will be made into a large partition called /data
- we will move your data (Libre office documents, email, web browser bookmarks etc.) to /data
- from now on you can burn a backup of your data directly from /data to CD or DVD
- Clonezilla can quickly make an image of the small partition containing Linux etc. to the larger /data partition. I do this monthly and can always get my PC back to the way it was working a short while back.
- You can burn this image off to a DVD for safe keeping
- Clonzilla can restore Linux, programs, preferences etc. if something gets goofed up.
- If your hard drive dies you can build a new system from the image and data CD/DVDs.
It is not necessary to do all of these right now. If you want to start with 1 or 2 just let me know. I have Ubuntu installed on a test machine similar to your PC and I can walk through this with you step by step.