How to Identify Capacitor Values in Schematics

It makes sense that pin 8 is connected to +Vdd. The pin is labeled with that in the datasheet and notice the 100uF (in parallel with 100nF for high frequencies) capacitor to decouple power supply from pin 8 to ground.

R1/R2 form a voltage divider that biases both amplifiers at half the supply voltage so you can suffice with a single power supply (and in- and output capacitors in the signal way).

It seems that the author of the diagram just forgot to include the power supply itself.

You must be looking in the wrong place. Go to digikey.com and enter the appropriate parametric search, and you'll find all the components you want: http://www.digikey.com/product-search/en/capacitors/ceramic-capacitors/131083?k=capacitor

Substituting capacitors used for bypassing can work just fine; typically more is better in those cases (as long as ESR and voltage rating is sufficient.) Substituting capacitors used as part of a tuned filter is much less straightforward. Thus, to answer your question, we need to know the role of each of those capacitors.