#1:For case fans check them:
#2: if you want you can run memtest86 bootable CD(download ISO file from http://www.memtest86.com/
extract the zip file, burn iso as an image, pop in dvdrom, boot from it). One run should be enough to see if RAM is stable.
#3: It depends on what voltages it is running now on. If it is up to 1.35v then it is ok as it is. If higher, then it needs changing to lower than 1.35v)
#4: 40C is too high if you want to overclock the CPU. It is fine at stock clocks, but not for overclocking. I take it you are using cooler which came with the cpu. For overclocking you need aftermarket CPU cooler.
AMD Phenom II X6@3.9ghz<>MSI 890FXA-GD70
8Gb OCZ 1600Mhz cas 7 RAM<>AMD Radeon HD6970
300Gb WD Velociraptor<>2.5Tb HDDs
CM Cosmos S<>Custom cheap watercooling
Win 7 Ultimate 64bit<>32'' 1080p TV