New to building desktops, need help buying parts for a gaming computer

Solution
I adapted a build I suggested in another thread, this should be good (probably even overkill on the GPU) for you.
Have the HDD's in RAID1 and that gives you your disk failure protection, though it means that you have 2x1TB drives for an effective 1TB of storage. Backing up to an external drive is always going to be the best solution, if annoying.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-4570 3.2GHz Quad-Core Processor ($229.00 @ Mwave Australia)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($39.00 @ Mwave Australia)
Motherboard: Gigabyte GA-H87M-D3H Micro ATX LGA1150 Motherboard ($109.00 @ CPL...
I adapted a build I suggested in another thread, this should be good (probably even overkill on the GPU) for you.
Have the HDD's in RAID1 and that gives you your disk failure protection, though it means that you have 2x1TB drives for an effective 1TB of storage. Backing up to an external drive is always going to be the best solution, if annoying.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-4570 3.2GHz Quad-Core Processor ($229.00 @ Mwave Australia)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($39.00 @ Mwave Australia)
Motherboard: Gigabyte GA-H87M-D3H Micro ATX LGA1150 Motherboard ($109.00 @ CPL Online)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-1866 Memory ($99.00 @ PCCaseGear)
Storage: Samsung 840 EVO 250GB 2.5" Solid State Disk ($179.00 @ PCCaseGear)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($69.00 @ PLE Computers)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($69.00 @ PLE Computers)
Video Card: Gigabyte GeForce GTX 780 3GB Video Card ($579.00 @ Mwave Australia)
Case: Corsair 350D MicroATX Mid Tower Case ($139.00 @ PCCaseGear)
Power Supply: Silverstone Strider 600W 80+ Silver Certified Fully-Modular ATX Power Supply ($109.00 @ PCCaseGear)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($115.00 @ Mwave Australia)
Total: $1735.00
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-04-05 20:21 EST+1100)
 
Solution
Future upgrades, really depends what your going to be doing. For now, its a good gaming rig and a decent workhorse.
Theirs nothing in particular that would hold you back from upgrades other than not being able to Crossfire/SLI on that board and PSU and maybe custom water because of the relatively small case.

Probably partitioning the SSD and installing Linux on that partition. Have it set to boot to Windows by default, and when you want Linux, hit whatever key (for me its F11) during the mobo splash screen to bring up the boot menu, from there you can go Linux.
At least thats how I would do it.