Found a diagram for it at:
Looks pretty much the same as the Gaggia Espresso, but according to a thread on coffeegeek, the Dandy has the three way valve (and the parts schematic seems to confirm this). Assuming this is the case and it actually works, you got a seriously good bargain. Youve pretty much got a Gaggia classic in a plastic case.
My suggestion is to tune the over pressure valve to approximately correct pressure and install a PID (or have someone install one for you). If you like milk based drinks, a Rancilio steam wand is a useful upgrade.
Plenty of threads here and on other forums for ways to tune/modify your Gaggia. Ill also be happy to answer questions you may have, to the best of my ability.