gear swaps are not cheap. they are cheap-er if you can do them yourself, but it's not something suggested for a beginner.
car-part.com can most definitely find you some ZJ front axles with 3.73 gears and that axle will bolt in.
you'll essentially need a 4wd Peugeot for the parts to make a 2wd Peugeot into a 4wd Peugeot. but yes, a 21 spline t-case will bolt to it.
but I'd rather invest some money and get an AX-15 with a 23 spline t-case.
gotta have patience. it's a holiday weekend.
I did some searching and found info on previous years but not this upcoming one so maybe they haven't picked a weekend yet? If I see anything, I'll be sure to pass it along.