As IRONBATMAN already stated the laptops are an all-in-one deal, even if it wasn't soldered there are not laptop gpus for sale that i know of, the parts are usually custom and smaller versions of desktop sized parts, althought a gt 750m shouldn't be bad, it is a quite new card, now as the overclocking you mentioned, i wouldn't recommend that too, laptops don't have big heatsinks or a big space to dissipate the heat (gaming laptops even have a hard time controlling themselves at market clocks) so overclocking can turn out bad....sorry for the bad news
P.S. i am open to corrections of any kind 😛
Happy Gaming! 😀