SnailVendor wrote:
I'm assuming the GPU, CPU, Screen, DVD drive, WIFI card and RAM still work fine (and I've already removed the HDD to turn it into an external HDD) so I was wondering whether it would be possible to reuse those parts to save me some costs in building a proper gaming PC?

Quite an assumption since it's a dead machine and "the guy at the repair shop" told you "the motherboard suffered a serious short-circuit". Any component salvaged from an electrically-damaged mainboard is automatically compromised and has dubious reliability. There's a reason the thing won't even turn on anymore. I would expect some sort of evidence supporting such a serious technical diagnosis - maybe point out some of the burnt/killed hardware components, maybe a photograph showing ugly damage, etc - it kinda sounds to me like the guy wasn't interested in even doing the job, didn't know how or didn't think it would be profitable enough, etc. From a customer perspective it's unreasonable to pay more for a repair than the cost of a replacement - and replacement G551JX parts might be available inexpensively if you do some digging.

Laptops typically have certain modular components - like memory and storage - which can be swapped out and used in other machines. Many have internal parts with standard form factors - Mini-PCIe WiFi card, GPU MXM module, etc - which could be swapped out and used in other machines. The battery can also be used in other laptops within the same laptop brand/model/family. All other parts are usually fully embedded (permanently soldered in place) or follow standard form factors (display panel internal DP ribbon, mobile processor socket, etc) but have hardware specs/quirks which are incompatible with the vast majority of other laptop models/variants.

You admit that you don't have knowledge or experience with building PCs. Attempting to salvage parts from a dead laptop is not the best place to start - it's a technologically dense machine packed with clever engineering, merely taking the thing apart and putting it back together (properly) will be a challenge for inexperienced people, while troubleshooting hardware faults and extracting internal parts (which aren't easily accessible through chassis access panels) will effectively be impossible. Desktops and laptops basically use completely incompatible hardware - and even if you could turn your laptop parts into desktop parts (it's not impossible if you understand PC hardware and some electronics) you would find that it's not worth the effort. After all, your laptop died and won't even turn on ... and it's out of warranty so it's basically "old tech" which won't make a great gaming computer ... and in the end this sort of project would basically cost you more than the price of a new (and working, and better) computer.

I advise donating it to a charity like Free Geek, or simply sell it on eBay (as a "dead, for parts" machine). Either way, your dead paperweight might be repaired, refurbed, reclaimed, recycled, and repurposed ... and you can already forget about making money from it, if what you've been told about it is true then it already has effectively zero value. You might want to take it to a different repair shop to get a second opinion, indeed you might even be able to sell it to them ("for parts") or trade it in as credit towards something else.

Thank you all for your replies and your great insight. As Koth suggested I took it in to a different repair shop for a second opinion and got pretty much the same conclusion. Guess I'll see if anyone on Ebay wants to buy it otherwise I'll look at donating it to a charity or recycling it.

Thanks again!

The drive(s) and RAM could be used in other laptops. The CPU and GPU might also be useful in other laptops - if they still work, and if they're socketed/removable.
The battery, screen, and keyboard could be used as replacement parts for other ROG G551 laptops. (Any part could be used as a replacement, if it still works, though these are the parts which most commonly fail/break.)