For some background, I have a 2014 Alienware 17 R1 Laptop. And for the past couple months, I’ve had a lot of problems with the HDD (1TB) always running at 100% and the computer would slow down a lot. I tried many fixes and they would only bandaid the issue, not too recently though, I would have a blue screen error (REFERENCE_BY_POINTER) happening like every 15 - 30 minutes on the computer.

I have tried everything and I’m convinced I just need to replace the old HDD with a new internal SSD. My only problem is, I don’t know what SSD in particular I need to use to replace in the computer. I have seen ones that look like small NVME / SATA chip forms and ones that look like bigger Square box looking ones.

All I really need are some SSD recommendations (500 gb preferably) and, if you know one, a disassembly/assembly video only if you have one. 
As my username says I’m fairly new to this, so any and all help is appreciated