Inspiron N7010 Upgrade

I've had my beloved Dell Inspiron N7010 for 6 years. Since my warranty expired I've upgrade the RAM. My current graphics card is AMD Mobility Radeon HD 5000 Series. I'm not trained in computers per se, but I've done several repairs on various laptop/desktop models as necessary. I'm aware that I'd need to replace the mainboard in order to upgrade the graphics card.

What I need to know is how to find and order such a replacement as would work best with my laptop case. I understand most people would just buy a new laptop, and I do already own another laptop as my backup. However, I'd like to know what options I have available before I give up on my favorite trusty laptop.

It's not just a desire to upgrade, but also because the card seems to be glitching out more and more frequently. So please help!