This should be very simple to do:
Firstly, you record the sound in mono, and make sure it is in PCM (Pulse code modulation - **broken link removed**. You don't need to strip the header, just save the file to an (E)EPROM. The header is so short, It won't be audible. You can get quite big (E)EPROMs.
Make a clock source with timing equal to your sampleling rate.
Feed the clock to a binary counter. Make sure it matches the address-space in the EEPROM. You can cascade counters easily, a neat little trick.
Feed the counter to the (E)EPROM.
Feed to output from the (E)EPROM to an 8-bit DAC (linear). But make sure then that you also record with 8-bits. 16-bit DAC you can use with 16-bit recordings.
Then amplify the output from the DAC.
To reset the playback, simply reset the counter, or kill power to the counter. This will work because of the way PCM works, and the way linears DACs work (**broken link removed**.
If your interested, you should also have a look at sampling theory.
If you need a better sound quality, you need to put in a low-pass filter. Cap at 11250kHz or lower, or what ever you sample at.