If Windows 10 was activated on your system, you will not need to know the Windows product key. After you install Windows 10 on the new drive and connect to the Internet, Windows 10 will automatically reactivate. If you have a hard disk drive, as you said, then before you proceed I highly recommend that you replace it with a SSD (solid state drive). A SSD will be much faster and you will notice the difference. When you're ready, here is a post I wrote about how to install Windows. Here's another description of the install process, from a Microsoft MVP. Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard.
I have a 2016 Precision 5510. The HDD has failed and i have been trying to use the DELL OS RECOVERY TOOL to restore it to factory defaults. If i try to create the USB on a separate PC I was able to create the bootable USB but the restore just hangs on a black screen with only a mouse cursor I have also cloned a drive from another dell to boot the machine, which allows me to install DELL SO RECOVERY directly on the machine. In this method it downloads the file and then says "verification was unsuccessful" Does this tool ever work for anyone? Or am I just wasting my time? thanks, Quinton  
Precision 5510, Dell OS recovery tool can't restore OS