If you have low current, yes. Unfortunately, they don't describe it very well, but it should be possible. Try it out. Just a note though. Sometimes, opamps pull a little more current in certain areas of operation. So you may have trouble getting it to charge up even if it works if it is connected after being fully charged.
That depends upon what's powering the MAX232, which is (if I remember correctly) an RS-232 type interface IC.
If the MAX232 is in use, you will likely find that the power pins have a good deal of noise on them, which is usually not a good thing for opamp circuits - they may still work, just not like you expected them to.
If you want a decent and cheap bench supply, salvage an ATX form-factor power supply from a junked PC and build one from it. Google: "ATX Bench Supply" for lots of plans.
thanks. I tried to hook them up to an instrumentation amps INA126 and measured output from a thermocouple, it worked fine. but it doesn't work with a thermocouple calibarator.