Typical of most (all?) employees in so-called electronics stores these days, they could find their arse with both hands and a map. Now if you had a question about a laughing clock or toy helicopter you'd be right.
He said it was a voltage regulator
About as wrong as you can get.
has the exact same function
Wrong again.
The 741 is an opamp, I grant that it can be used as an inverter but it is not an equivalent to a 74xx14/04.
I think you need to find a new shop :), actually don't bother, I think they're all the same these days.
This is what you need
http://jaycar.com.au/productView.asp?ID=ZS5004&keywords=74ls04&form=KEYWORD
or
http://jaycar.com.au/productView.asp?ID=ZS5014&keywords=74ls14&form=KEYWORD
Have you ordered your logic analyzer yet?
Rob