Manequin Skeleton Important Question

There are many human models that you can buy on the Market Place and many of them are rigged to work with The Manequin Skeleton. That means you can use a lot of animations and that is wonderful. But now to the question - If you find some models that you really really like - but the arms are to big or the hands are to big for tour liking - Is there a way of changing this yourself ?

The example in my case is this on the Marketplace : NPC Characters Female (Pack)

I like the clothes and the look overall - but both the arms and the hands are to big so I would like to make the arms shorter and most of all the hands smaller - would be very grateful if anyone could tell we if it is possibly - and in this case - what is the best way to do this ?

Kind Regards