New Hard Drive help

Hey guys. I was hoping someone could help me. Recently I've had horrible trouble with my laptop. Long story short I'm having "Reallocated Sectors Count" and "Current Pending Sector Count" issues so my hard drive is dying.

I'm looking to replace my harddrive in my PC as a cheaper option than buying a new laptop entirely but I'm concerned about my OS.

If I swap out my hard drive will I need to rebuy Windows 10 or will i be able to get Windows 10 on it another way?

I've never done this type of thing before so any help would be appreciated. Thanks.