I have an Acer Aspire 4830tg with an integrated Intel gpu and a Geforce gt540m gpu. I'd like to replace the Geforce card with something more powerful, but I can't find any info about how to do it or if it's even possible.
The motherboard is an InsydeH20, model number JM40_HR.
In general, the answer to "can I upgrade my laptop's GPU" is almost always "no".
Only specific laptops, like those from Sager/Clevo, MSI, or Alienware usually have standardized upgradeable video cards (MXM), and even those are usually only their high-end 15" and 17" models.
It is possible that other brands and models might have a proprietary video designs which allow replacement, but these rarely allow "upgrade" unless the same model shipped with a superior GPU in more expensive models.
Even if a superior model existed... this is a 14" laptop from 2011. You aren't going to get much better than a 540m in there.
Given that this is an Acer 14" value-model, I sincerely doubt it.