building a comp is like playing with blocks as a kid. everything will only fit in one way and in one slot. a monkey could do it. the only bit of luck you need is to not ESD anything and be lucky enough to get parts that work together with out needing to tinker. os installs are guided now days so its not hard to install one once the hardware works.
SSD's dont open many more maintenance issues unless they are going into a raid, then you open up quite a bit of this but not that and that but not this unless that (stuff). if you are going to run a single SSD then trim will handle most everything you need so long as you dont get a crappy SSD. i have had very poor experience with OCZ's failing or dropping power, randomly not being detected or loosing file systems all together. I have 3 intel drives that have been running 2 years now with absolutely zero issues. the only issue i ran into with them was a cable issue where the plastic on the sata cable cracked and the cable came out of the drive. Me being stupid at the time decided i must have a raid issue so i rebuilt the array before seeing only 1 drive was missing. had to do a data recovery on a raid-0 array after that.
anyway, single SSD's are fine but expensive. considering you are running low on space and not totally sure how to do backups or move things between drives you may want to play with that before getting one as that would be required with a SSD. I could not live with a C drive below 200GB so i had to get 3 80GB SSD's you may be able to live with a 120 but i honestly would not suggest getting anything smaller than a 120 unless you just surf the web.
I have been setting up raid 0, 0+1, 5,6,10's for many years and only encountered a raid issue once with a raid 5 and i blame the intel controller for that one. for the most part a properly setup raid can run trouble free until a drive dies. but when a raid fails it does take someone who knows what they are doing to repair it or recover data.