If it was a different pricing structure applied to "older" parts then the Part Number would stay the same. Cat Classic Parts have totally different Part Numbers to the "genuine full-fat" Part Number.
That would be the just the same case for genuine parts. The warranty cover applies to the parts themselves not to the labour required to remove & install them. If the part that failed caused damage to other parts around it then it would be up to the dealer who supplied the part to make a case to the manufacturer for goodwill support to cover the cost of the failure. That goodwill support might include a contribution towards the labour to strip and rebuild.
Usually Cat bearings are made to Cat designs and are somewhat different in size to standard bearings. You may get lucky though and find something that fits. I would use a genuine Cat gear rather than a Classic TBH.
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That's why if you look at a bearing that comes out of a Cat box it will generally have "Cat" and the Part Number stamped on it rather than a bearing manufacturer's name and a standard bearing number. As an example wheel bearings for the big off-highway trucks are made by Timken under an exclusive design agreement with Cat, let's face it they invested millions in developing the bearings, they're not going to sell them to every man and his dog afterwards. They will not sell that bearing to the world in general through any bearing supplier. Obviously that's a pretty specialized bearing but there are plenty of other similar examples.