I've replaced the RAM, wlan card and both hard drives in my 2013 Blade Pro. I used an MSata Crucial 480gb in place of the stock MSata cache drive, and a Seagate 750gb hybrid hard drive in place of the stock 500gb drive. The Seagate is slightly thicker than the stock drive - I had to leave off one of the HD bumpers. It fits so snug without it that I think it's safe. Both drives are accessible with Windows 7 - I use the MSata as a boot drive and the Seagate for media.
It wasn't too hard to do, just go slow and keep track of what screw goes where.