Don't be scared of overclocking, especially if you are looking to a new system.
It is only unstable with bad settings, you can fix that easily with a CMOS clear, which sets your BIOS back to normal, no more instability.
As for temps, 40c is pretty low and should leave you some headroom. You can get up to mid 60s safely (says intel).
Overclocking can give you a good 30% more performance out of that CPU, may as well try it out.
Its a good learning process about how your CPU/chipset work together and whatnot.