I took all the old parts out of the case and cleaned it up and about to put in the new ones, some help would be appreciated!
Anything particular I should be careful about while putting the motherboard into the case and all the parts on it?
I don't know what parts you're replacing, so I'm just going to give some general advice.
If your cooler has a bracket for the underside of the motherboard, it's usually easier to attach it to the motherboard first then put the motherboard into the case. It's up to you if you want to install the heatsink onto the motherboard before or after you put the motherboard into the case.
Don't use more brass standoff screws than the motherboard has mounting holes for. Some people think they should fill every hole in the motherboard tray with them so they can prop up the motherboard from underneath and prevent the board from flexing under pressure, but that's unnecessary and can cause short circuiting.
Parts should fit together relatively easily. However, sometimes the parts don't quite fit exactly due to varying fit and alignment, and a bit of elbow grease may be needed to get some things in all the way. A small amount of temporary flexing is alright for circuit boards.
Any particular I should look out for while connecting all the PSU wires to the motherboard?
Try planning a bit and exercising some cable management as space allows. Figure out where cables need to be plugged in, and the best way to connect them without tangling cables. Tie them down and out of the way, and try to tuck them either behind the motherboard or in an empty drive bay, or against the walls of the case if nothing else. It'll look nice, allow for more airflow and keep things tidy.
I'll be a GTX 970 and it seems there are 2 PCI-E ports on, do I need to connect both of them?
Yes. Your power supply should have a set of cables with connectors marked "VGA" or "PCI-E", only those cables fit the ports.
If not, the GTX 970 likely came with Y shape cable adaptors in the box. Don't connect both ends of the Y to the same power supply cable, connect each to a separate cable.
First time SSD user - should I follow everything from this guide
SSD Setup and tweak guide [SSDReview] ?
The guide looks fine. There are a few things to consider, though.
Disabling the page file can result in some programs, including some games, to refuse to run because the page file doesn't exist. Re-enabling the page file will fix that, or just keep it enabled but set to a low size (1~2GB)
Setting NO GUI may hamper troubleshooting efforts in the future. The amount of time saved is just a few seconds, so it's up to you how you want to set it.
Turning off drive indexing, windows search, write caching, and superfetch won't really impact SSD operation very much if at all. The guide author prefers that they be disabled, I prefer to keep them enabled. Again, kinda subjective and up to you.
AHCI and TRIM are the most important things to ensure are working for a SSD. Windows 7 and 8 should be able to detect that certain drives are SSDs and accordingly apply certain options, like TRIM, automatically. Doesn't hurt to check, though.
Is there anything to do other than setting everything up correctly? anything that needs to be doe in BIOS on first boot or in general? Any other tip would be appreciated as well. Thanks!
AHCI should be enabled and selected in BIOS before installing Windows.