How to choose the right amplifier for 100 Ohm RTD in 3 wire configuration?
Instrumentation amplifier is rather expensive. The input impedance is very huge, therefore it won't influence the wheatstone bridge. Further, what a RTD conditioner has to have is a low pass filter at input stage. You can place a RC filter on input, that again won't influence the bridge, since the input impedance of IA is unlimited. 
But there are ready made ADCs for RTD like ADS1248,...that are cheaper than a single IA.