I would make sure that you have created the recovery disks for your PC. Then I would get an external HD a simple plug and play one without backup software. Most of that is worthless. Then check out Paragon, EaseUS and Macrium they all have free versions of their software for making a disk images. You should be able to image the drive and reload it. I would image both the system and recovery partition.
Making a full disk image will enable you to carry the entire contents of your existing drive to the new one including all installed apps, user data etc which would save you a lot of time. Unfortunately it will also carry forward all junk, baggage, any malware, corruption etc. This is particularly undesirable if, as you say, the existing drive is showing signs of impending failure. Unless you have some over-riding reason to image and clone the existing drive I would go for a clean install which you may achieve simply by installing the new drive, booting from the recovery dvd and running the recovery to restore your new drive to factory settings.