Glad the SSD is working for you--great stuff! You're another vote for adding some life to the 'ol stock board so-to-speak (if you want to save money).
Changing the motherboard is pretty involved, in that you have to remove most of the internal components to pull it out (all your internal cards, fans, power supply, etc.) If you're comfortable with that level of hands-on hardware work, you'll be fine. I would give yourself a day at least to do the changeover and installation of any new motherboard.
The 630i can only fit a standard ATX-sized motherboard (no mATX or microATX, etc.), and the CPU fan at or less than the height of the Hyper 212 Plus/EVO (159mm) to fit in the 630i case--both use the same height heatsink.
Attached is a bit old, but hopefully still helpful how-to PDF I compiled when I switched to the ASRock P67 Extreme4 (though I later updated the doc to the slightly newer board, since they were so similar). It explains a lot more of the process--I hope it helps answer your questions!
If digging into hardware isn't your thing, you may want to consider buying a new pre-built system (plenty of good, fairly priced systems out there). Just let me know!