You're better off using an Mac-supported cards from Apple or others.
Apple's card are seriously outdated, both 5770 and 5870 are slow card in today's standard.
There "should" be a renew of Mac Pro some day, you can wait for that.
There are a cards like the Quadro K5000 that is Mac-compatible. But NOT out of the box. You need to install the driver first, and then install the card.
Also, support for AMD HD 7 series cards ARE NOT IN YET in 10.8.2. I had one of those in my old Hackintosh running 10.8.3, and it's still recognized as "AMD Radeon HD 7xxx series", so I will say wait for it.
Don't make any moves before AMD 7 series is out, maybe Apple or third-party will release cards for it.
Good luck!
It's very common for one component it's connected electrically to another component to cause noise and other issues. Whether it's the most likely cause is debatable, but Apple's service centers have direct access to engineering and a huge wealth of repair data so they would be my first authority to go to determine what is likely and what is not.
Without the detailed diagnostics from your specific repairs as well as the actual service manuals it's hard to second-guess Apple.
Apple provides a nice (IMO) warranty of 90 days and any repair, so it's hard to see how they would be scamming you. If you set down and catalog each interaction with AppleCare, have you spoken with them 10 or 20 times?
Also you need to collect all of the written estimates and repair details to know what components have and have not been examined by a technician.
The only time I've known Apple executive relations to be unable to resolve A customer issue is when Apple has already bent over backwards to accommodate their responsibilities and person requesting the repair is the one being unreasonable. I certainly wouldn't accuse you of that with the little data presented, but if you really still unsure collect the facts and data you have and give it to someone who is somewhat impartial and have them give you their opinion.
Also, a final note - unless you are running stock OS or an apple benchmark, I've seen all sorts of gfx card mods and graphics tools cause exactly what you see. My guess is Apple knows other parts to be good and is guessing the trackpad is the most likely of the ones that remain in tested.
I would ask them the cost of a depot repair, and you'll have to be Ok with paying for it if they replace parts - even if the benchmark fails to run. If your Mac boots the normal OS fine, I would not pursue further repairs till the situation deteriorates.
Best Answer
Probably not, but you can use the ExpressCard slot instead
The model you mentioned (17" MacBookPro8,3 late 2011) does seem to have a separate Wifi/bluetooth assembly, but you'll probably have a very hard time finding a matching replacement in both size and connection. I didn't find a disassembled 17" model, but the card in the 15" of the same generation looks like this (4 antenna connectors and what is probably some sort of PCI Express cable).
However, since yours is a 17", it does have an ExpressCard slot, where you can stick in a Wifi card of your choosing (something like this) without even having to take the whole machine apart.
Or patch around your Linux kernel with one of the BCM4331 drivers that are out there, but I assume you've already tried that.