You needn’t worry about PCI Express 2.0 or 1.0. They’re backwards and forwards compatible, and there’s little noticeable difference in performance.
I would’ve replaced the mainboard - It’s using an old chipset and it isn’t even the good incarnation of it. There’s this, which is what I use. It’s a solid board, but don’t expect to do any overclocking. If you want to stay Gigabyte there’s this, which is about equivalent to what you had picked, but with a more recent chipset. It’s not a necessity though as what you’ve picked will work just fine.
What were you planning for RAM?