18 R1, need advice for upgrading (noob here)

Hello fellow forum users! I am the owner of a very old Alienware 18 laptop that I bought about 7 years ago and it has never been upgraded. Now before you say I would be better off buying a new rig - no, this is my beast of burden and I would like to keep it as such (also I think it would be cheaper). This was my first gaming PC and as such, I have never had the opportunity to really learn the ins and outs of computers, so that is why I have come to you for help and guidance. My foremost issue is I would like to upgrade the GPUs (my rig has two). When I bought my rig I was able to run current games and future releases for the next few years at max settings however as games evolve the hardware required to run them does too. My ultimate goal is to have my computer ready for Cyberpunk 2077 but as that is not out yet, the Witcher 3 at Max Settings, or close to it, is my benchmark (I currently struggle to play even on low settings). Could someone recommend some high-end GPUs that are compatible with the Alienware 18 (I am not sure which revision I have, how can I find this)? And with upgrading the GPUs will I also be required to upgrade the CPU? If yes, what are some high-end CPUs I should look at? I do not know much about clock speeds, cores, etc. so any relevant information on that would also be helpful. Is it also recommended that I upgrade (or at least buy new) fans to compensate for the increase in temperature thanks to the newer hardware? I use a fan cooling pad under my laptop but I would hate to upgrade my computer just to have it combust. What else, if anything, needs to be upgraded so everything is compatible? Below I have attached my laptop's specifications. If you require any additional information to answer my questions please ask and I will retrieve it. I apologize for such a long post with many questions but any help or advice you can give me would be greatly appreciated! 

Thank you!