This answer is entirely dependent on whatever sound editing program you are using. With a normal single-track editor: copy and paste the exact same info into both the left and right channels. Then use either a plug-in or the program's dsp to add reverb (best) or chorus (too phase-y).
But your best option would be to get a multi-track editor (ProTools free if you run a Mac), mix the mono track slightly off center, and then use some aux inputs to add stereo reverb and mid-range delays.
Anyhoo... if you have a Mac a reccommend downloading ProTools free at www.digidesign.com. This will also work if you are running Win98 on a PC. But a better option on the PC would be SoundForge 6.0 at www.sonicfoundry.com. Their plugins are not too bad.
Hope this helps! I've done this before so let me know how it goes.