I found a front axle from a '97 sidekick 4 door.  It should have 26 spline front axle shafts, correct?  If so, how much are they worth?

It should have 26 spline shafts. As for how much it's worth, that depends on condition of the CV's, boots, shafts, splines, etc. How much of the front axle are you wondering about a price for? Hub to hub including the front third? Locally the price I can get those for from a decent salvage yard is $75 for each CV shaft and another $75 for the entire front third, housing and all....

I was wondering mainly about just the axle shafts.  If I understand it correctly, the axle shafts can be swapped into a 22 spline front, if the sidegears in the carrier are changed, right?

Yes,  but to get the side gears you need to
buy the 3rd member, so you might as well get
the whole thing, it's not a good idea to swap
diff parts, even just the side gears, if the ratio
is the same, use the whole axle, don't swap parts
it's a PITA to get in and out, as well as the axle, get
the mounts too, there are 3 bolt and 4 bolt side
mounts.

Wild

You can buy the 26 spline sidegears from your local suzi dealer,Thats what i did when i upgraded to 26 spline cv's.