Ok , ill explain , if as mentioned previously the laptop in question uses a BGA type graphics card this is soldiered directly to the motherboard to replace a graphics card on this type of motherboard you need a special BGA Re- soldiering station capable of reaching 220 odd C or will need to find someone to pay for this some people have been known to build their own re-soldiering stations and buy all the equipment to do this but its just not viable for most people .
They will then strip the laptop down into its component parts and essentially rebuild the laptop melting away the old card's connection replacing it with a new one and rebuilding the laptop , price wise to do this after you have bought a suitable replacement card wont be far off from a brand new better laptop , however this may also require some software engineering as the systems bios may not accept the new card if it is too different from the old one .
So the rule of thumb is ... if you want a better graphics card in a laptop you can build your own EGPU setup this is a sort of external dock housing a dedicated graphics card and some clever software to mcguyver a better graphics system onto the side of the laptop .
If you want to find out about this read here but this is pretty technical stuff ( sorry for offsite link)
http
/www.techradar.com/news/computing-components/graphics-cards/how-to-make-an-external-laptop-graphics-adaptor-915616