Wheel/base swaps can be achieved fairly easily without destroying the casting. Rubber tires are the easiest as they can just be removed and replaced. Plastic tires would require the drilling of the rivets on the base to switch the base to a rubber tire version or to swap out the plastic tires for another axle. Then you just need to reattach the base to the body with screws or glue. While you have the base off you can also swap out interiors!
The rubbers pull off as mentioned and if i remember correctly, will have a seperate rim and a wheel retainer still on the axle. If youre good with a dremel you could try grinding away at the axle head without tearing the car apart. A little JB should work just fine if you want to reuse that axle, as long as the axle rolls freely in the chassis ('weld' the axle inside the retainer, carefully) . I usually just cut the axle just behind the wheel and use a new axle from a donor or use a straight pin cut to size. You might have to enlarge the groove in the base a bit either way. Some use solder to make a new head for the axle (ive never tried this).
The plastic tires are like Hot Wheels. Unless youre good at grinding the axle heads down, youll have to tear the car apart. Again, i usually just cut the axle right behind the wheel and be done with it. Sometimes the tire is part of the axle with only the rim being a seperate piece. The tight fit on some of those rims is crazy. Id say that half of my attempts led to a busted rim or tire that was marred beyond saving. I did just that with a Duster and had 3 good rims and 1 that came out in 2 pieces. If you can get the rims out, sand the ridges off so you can install and remove if you have to. You can always glue it back in later.
It should be a no-brainer but ill say it anyway, dont forget eye protection and a few bandaids just in case. Saftey first.