For op amps, usually the letters/numbers after the main part number have to do with either package type (DIP, SIP, SOIC, etC) or operating maximums (how hot/cold they can get before failing). And occasionally, they denote something like max voltage. So you can almost always safely use op amps that only differ by the trailing letters/numbers. So TL072 and TL072CP are both going to work fine in 99% of effects circuits.
Other ICs may vary a bit more, but usually it's still the same kind of thing. The LM386-N3 is a good example. It's the same as the LM386 or LM386-N1, but it puts out a bit more volume/gain at the same voltage.
As was suggested previously, always google the part number and check out the first couple pages of the data sheet to verify.
