Envy 17 3D vs non-3D - a few questions

Hi people. I am looking to buy a 17" multimedia laptop and seems like the Envy 17 is hard to beat for it's configuration/looks/price. I am currently the owner of a Dell Precision M6300 ( x9000/1920p/3600M ).

I am looking at Manufactured Refurbished offers and I have some questions.

Do the 3D models have the options of swapping video cards? I will use my laptop on the go so most of the time I will not need the blastering power of the dedicated video card. If the answer to this question is related to the CPU/GPU models - I am looking for example at a 3D model with Core i7 2630 / Ati 6850. Also related to the 3D models - do all 3Ds come with full-hd 1920x1080 screen or there are some with the 1600x900 also. I know the non-3D models can be equipped with both. I am really not interested in the 3D capability because I will probably not use it that much. Besides the obvious benifit of 3D, what are other pluses or drawbacks of having a 3D vs non-3D model.

Also what's the deal with Beats audio? I have seen that some Envys have a red border around the keyboard + the red volume knob. Others don't but they all state to have the Beats Audio speaker system.

Anything I should be careful about when choosing the right Envy in terms of CPUs ( which ones are clearly better etc ). Also any specific preference between the ATI 6850 or the 7690M XT?

What about the heat/shutdown problems a lot of people are talking about. Do I need to cut/open the laptop right after I get it to change the damn termal paste ? I understand there are some differences between 1xxx, 2xxx and 3xxx models. Care to elaborate ?

Sorry for all the dumb questions but I have never seen a live Envy 17 and Google isn't always helping right on the matter I am intersted in.