I have a 6GB system, will it be okay if I use the 4GB mod?
Will it not hurt my RAM or my system in anyway?

Thing is I have 3x 2GB = 6Gb and one of those has been broken, and I ended up using 4GB until fixing it recently. So I did not know what the issue was and thought I should just make sure.
And I am not tech savy or whatnot so I thought Id play it safe.

Thanks

You can use the 4GB mod. It has nothing to do with the physical memory in your system. The question is do you need to. It generally used if people are loading on the mods/textures/replaacers/etc
and are exceeding the 2GB range the game normally is under. It has also helped people with crash issues and startup issues. The 4GB mod is for people with 64-bit versions of windows also.

well I have a few mods, but not replacers. So I dont know. I am also using the 64bit version.
I do notice an improvement when I use the 4gb mod, the game becomes much smoother

Yea then go ahead and use it. It wont hurt anything and you have plenty of RAM.