Circuit for precision electronic balance

Hello everybody!
I found this two links that describe making a precise laboratory scale for weighing things in the mg and microgram range.
Because i'm not familiar with the field of electronics i ask you could you look at the circuit and say if the would really work like the would say, and in the second page there is also a microcontroller would i have to program it? And lastly how much do you think the different components would cost?

Links:

Homemade Microgram Electrobalance

Scientific American: Down among the Micrograms

Thanks for the answers!