Re: upgrading GPU
No work around. Mainboards are not generic on laptops like they are on desktops. There is no ATX or Mini ATX for laptops. They are all manufacturer specific.
So you would have to find a mainboard that fits in your case, meaning it would have to be made by the same manufacture and would have to be the same class of laptop (IE presario). Then if you did find that it would have to support your other de vices like your wireless, monitor, keyboard, ext. Have you ever taken one apart? They are EXTREMELY specific and very from laptop to lapotp.
So your only option would be to purchase another motherboard that would have been made for the exact same laptop, but the upgraded model. In that case you are still looking at around 300 dollars for the part alone.
GPU's on laptops are tricky, 9 out of 10 require a mainboard swap as you've eluded to, but you can't swap the mainboard because mainboards are specific to case.