A final nasty that sometimes crops up is 50Hz/60Hz hum or buzz, stemming from an earth-loop problem when capturing the sample. It's best to re-record, but if you can't, simple notch EQ won't solve the issue. Instead, use a comb-filtering plug-in such as Tone Boosters' TB_HumRemo...
2, I produce easily with 16GB of RAM but if you'll be multitracking (recording lots of channels at once) or using large plugins disk speed is much more important so SSDs are a must. Personally I use HDDs for my massive plugins but the loading time for some large (70GB+) KONTAKT li...