[simpits-tech] OPamp question

[Jeroen Huijben]

I have a small OPamp circuit for a loadcell that has adjustable gain and 
offset. (similar to betainnovation's X-amp)
I need a another one and I want to build it myself.

It is designed to be connected to a joystick PCB with VCC (5V), Vout and 
GND.
The loadcell needs VCC, V+, V- and GND.
Amplification should be from a few mV to 5V. (1000x)

Careful scrutiny resulted in this schematic:
http://members.chello.nl/~jhuijben/opamp%20circuit.gif

I have some questions.

What values should the pots (gain and offset) and capacitator (c1) have?
The resistor on the board that I have is 18 +/- 0.9 Ohms.
How would different values influence it's behaviour?

I have been looking around for OPamp circuits and I found one that is very 
similar.
The difference is that in that one V+ and V- attach to the ends of the pots 
(where mine has GND) instead of between the wipers and the OPamp.
Would that work or have I missed something?