your gopro footage is probably in mp4 format. you can transcode to dnxhd or prores and it will be alot more edit friendly, possibly allowing your laptop to work. transcoding will increase the file sizes, so you may need to use a large external hdd or ssd to hold the media. if you bought a 2 core i7 laptop, those will be slow, about half the speed of the 4 core i7's. the 4 core i7 laptops should be able to edit the transcoded footage fine.
none of those on the costco's webpage are balanced for premiere, more for gaming. the one you list is close, but the 64gb ram isn't needed, adding $300-400+ to the cost. the rest start getting into gpu's that are for 4k gaming, that would be overkill for your hd footage. either way, you are overpaying for ram or gpu from those computers. the 2tb hdd may work for the mp4 files from the gopro, but for normal/larger format types, a ssd or hdd raid would be better. there are some i7-5820k +16gb ram + gtx 960 computers for around $1500 from hp and CyberpowerPC, that should work fine for the gopro footage. if you can find those at a store near you with an easy return policy, thats another option.
Tell us what laptop you have and exactly what media you have, there is a difference between different GoPro models. I have a laptop and while I do not have that much of my son's GoPro 4 footage, I do have some. I have tweaked and tuned this laptop a lot. Maybe here is hope for your laptop.
I am editing three Sony camera AVCHD 1080 timelines with very smooth results.
Our Premiere Pro BenchMark (PPBM) can test your laptop and we may be able to help in that respect.