IQ input data from GN3S Sampler v2

Hi all,
I'm new to the world of low-level GPS, so please bear with me if this
is a stupid question.

I have the version 2 of the GN3S Sampler.  It's based on the SE4210
front-end, and outputs 2-bit I/Q data at 8.1838MHz, with a near-zero
IF.    I can get the data off the stick, but how should I go about
adapting it into a format suitable for SoftOSGPS, which presumably was
designed to work with the sign/magnitude data output from the first
version of the GN3S?

Thanks very much for your help,

Henry Hallam