OK, I'll be the doubting Thomas...
Is this a Toyota dealership or a used car dealer?
Axle jobs can be done wrong or not enough done.  

one right, they retail for about $1,000 not counting rebult birfields which may be what he is talking about since there is not much else to remanufacture. For a dealer selling a truck at that price I would suspect shortcuts even with a good dealer reputation. Get them to give you an invoice writing down exactly what they did to the axles, what parts were replaced/rebuilt including seals and bearings and post their explanation and parts list here. An accurate parts list is critical. We will then have questions for you for the mechanic.
For the lockers, I am surprised they are replacing the motor. Those things tends to loosen up if never used but it takes time and you need to be on gravel and weaving a little. Most likely they just took it out on some gravel and got it loose. I'm not sure I would believe them unless I saw an invoice for the motor.
If the seats are perfect after 168k that is pretty surprising. Somebody sat in the driver's seat for 168k after all and the leather in these things does not usually hold up. If it seems too good to be true, be careful. Have you Carfaxed it to see if it is a rebuild /salvage?
For $10,500 it depends on the year and where in the country you are, but with that mileage and lockers I'd say a fair deal, and maybe pretty good if they just redid your axles properly.
Main mechanical issue with the truck at that mileage is head gasket. Check radiator to see how clean (they gunk up which leads to overheating). Check around the head to see if any crusty build up or to see if recently shampooed. Take a look at the overflow tank.  

oes it need fluid?
BTW nothing wrong with adding a K&N filter, but I would not try to squeeze any more hp out of a truck with that mileage, and I would get a compression check. Your motor is just past middle aged and should not be raced or thrashed. Treat right, it should be good to 300k.