hi,
Looked thru your links, they recommend a 1 VppK signal.
The 555 timer driving the push/pull pair into an inductor/cap giving a 'sinewave' would be OK.
I would suggest a small audio transformer would give you sufficient drive for the Sensor ie; 1 Vppk.
Power the 555 from a regulated supply, say +5V, keeping the bridge excitation constant.
You will have to adjust the value of the inductor/cap to suit 1KHZ, rather than 50/60HZ,
to give something 'like' a sinusoidal excitation waveform at 1KHz.
Use a 'ac' coupled OPA, with a bandpass filter for 1KHz, the output into the FWPrec OPA circuit.
Design for 0v thru +5Vdc into the PIC's ADC, for the maximum range of the Sensor bridge.