I have heard a little about overclocking, but I don't know much about it.
overclocking is basically running your hardware faster than the stock manufacturer set speeds. in some cases (mostly in video cards) parts may come factory overclocked from the baseline stats. you get better performance however more voltage is drawn and more heat is generated. in many cases it is a good tradeoff. overclocking too high however can cause artifacts (anomolies) or in severe cases can cause the part to fail. overclocked parts do not necessarily fail sooner than stock parts.
It is easy to overclock the CPU?
provided you have an unlocked cpu (such as the intel chips ending in k) and an overclocking motherboard (like z77, z87) it is fairly easy and can be done in a few minutes. some motherboards even come with handy tools to help you do it easier.
In your opinion is it worth it to overclock the CPU?
i typically buy an overclockable cpu but run it stock. that way in the future i have the option of overclocking if i require extra performance. if i dont, i just leave it be. overclocking can give you pretty decent gains in the performance category provided you have the means to cool it and your power supply is oversized a bit to handle it.
If I were to overclock the CPU, would I have to also buy a better fan and heatsink for the processor?
yes. if all you want is a very mild overclock even a cheap hyper 212 can work however for heavier overclocks i would suggest something half decent. generally the bigger in size the cooler the better performance the heatsink. another option is a cpu water loop which relocates most of the bulk off the motherboard and to the fan ports on your case. you would need to have a case which supports the radiator on the cpu loop though.
And if overclocking is not that important, would you recommend the i5-4670?
if you do not plan on overclocking... then you dont need an i5-4670k therefore the normal 4670 would be fine. remember that you would then also not need the z87 motherboard and could go with a h87 to save cash. personally i go overclock ready and decide in a few years whether to do it or not (can always buy a heatsink then, but you need to buy the right cpu and mobo up front). your choice and either route is good.
Could you also provide links to some recommended motherboards for the LGA 1150 type processors?
if you plan on overclocking the asus z87 maximus vi hero is very nice an has many features for the fair price. the z87 sabertooth also isnt a bad choice but you would want to remove the thermal armor garbage (plastic covering on motherboard). of course you could go with a lower end board and do perfectly fine. asus has many decent products for less. if you want a 4670 (non k version) then i would probably go with an h87 asus pro. if you dont like asus then gigabyte isnt a bad brand (decent products, its just their customer service which is horrible in case of RMA).
Sorry for the deluge of questions, and thank you for a prompt response.
not really a problem. answering questions is why tomshardware forums exists.