For the 4940MX I think you're referring to the 17 g2, I'm looking at a 15 g2 which seems to have a 4910MQ listed as the highest CPU for that model. Now my question is it has a 4340 which is rated at 37 watts IF I put in a 4910MQ which rated at 47 watts is that going to be an issue?
No. When HP make the laptop/MB, they already consider the TDP so that they list that cpu, 4910mx, in the cpu support list. And you should use the 4340 to check your laptop BIOS to see it has the right version for the 4910MX, if the laptop does not have one, update the BIOS with 4340, then switch to the 4910mx.
Ok my second question is can I use a graphics card from dell to put in it? So let's say it's got a k610M and I want to put in a dell K2100M...will that work or does it have to be branded by HP for it to pick it up?