That's correct—the stairs were indeed made out of wood. They were of the same type that they put up to the PATH cars when on display at the Hoboken tracks.
The Acela Express does have two sets of emergency steps on either side of the train, that have to be removed and manually extended. IMHO, though, that was not a good idea to build them without the steps/trapdoors since that removes flexibility, not to mention makes them unable to stop at every NEC station (it limits them to the high platforms at Washington Union Station, also).
Acela Expresses are quite capable of using 25kV 60Hz, since they run on that voltage/frequency between New Haven and Boston every day. The "risk harming the equipment" excuse was a canard, IMHO...although the AE does have a bad reputation of ripping down catenary when the pans get entangled (whereas they are supposed to break away; that feature must not work as well as on other equipment).