You can start by getting the NI Daq Designer 2000. This will let you select the hardware you will need for your particular computer system. I would recommend the fieldpoint hardware and Lookout software as this will allow you to expand in the furture. It is ready for your type of environment.
As well, I would visit the website of Viatran or similar sensor manufacturers and select whatever type of weight cell you need. you can then determine what type of inputs you need on your fieldpoint system.
In closing, I will add this. Plan for expansion. You will be glad you did.