You might see a dip in performance - I went from Leopard->Snow Leopard->Lion->Mountain Lion->Mavericks on the same machine and so it would get better with one update, then worse, then better...I never made the jump across a few versions. The consensus seems to be that Snow Leopard to anything will cause a decrease in performance a bit, but Mavericks seems pretty friendly, especially with things like Memory Compression and Timer Coalescing.
I think in most cases, SSDs sold today are NAND. Personally, I like the Samsung drives, but the big difference is MLC/TLC vs. SLC. Since it is an older machine and MLC/TLC drives are much cheaper and still very reliable, you can save some money by getting a cheaper one. I think the mx100 is just a favorite due to price, performance, and newness. Someone else may be better to comment on that, since I've had more experience with the Samsung 830/840/840 Evo/840 Pro models.
RAM installation is super-easy in all of these machines. Once you're in there, it basically snaps in place (just be careful not to break the tabs off the clips that hold it in place. According to MacTracker, yours uses 2 - 204-pin PC3-8500 (1066 MHz) DDR3 SO-DIMM and will take up to 8GB officially by Apple's specs, but people have had success with 16GB. Just about any RAM fitting those specs should work, so it may just depend on price/preferenceOther World Computing is a favorite due to their knowledge of Apple products and excellent service:
http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3
In theory, the SATA II bus would be a limiter. Right now with a spinning hard drive, you wouldn't be able to even max it out. With any SSD, you'll see a noticeable difference. I'd get a SATA III drive in case I ever decided to use it somewhere else (in other words, don't buy an SATA II-only drive). This video might help show how any SSD will outperform a hard drive - although they're 15" models, the 2010 model has SATA II (3Gbps), while the 2011 and 2012 models have SATA III (6Gbps):
https://www.youtube.com/watch?v=Ki6TQByNm24