I have about a 1" stub of exposed PVC piping to work with. Should I install a coupling and another PCV pipe before gluing on the slip connector, so I have pipe to work with in case I need to in the future, or just glue the slip connector onto the 1" stub? Or should I do something different before installing the PTrap? Thanks.

You want to know what I would do - or rather, what I actually did when I had a similar case? I used one of these: http://www.hardwareworld.com/Drain-Trap-Connector-p7OAK2B.aspx
Like this, nothing is permanent, since no glue is involved, only those silver "hose" clamps which can be easily loosened or tightend with a screwdriver or nutdriver.

Oh, and you can pick that piece up at Lowe's (you don't have to buy it online).

Have fun!
Moishe
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