These GS cross spoke wheels are not really a DIY job, so I would forget about doing it yourself.
It is possible with the right gear and a bit of bodging but if it is not obvious to you at first glance why you can't rebuild them like a normal wheel then it is unlikely you will be able too.
Quite a few claim to have rebuilt them , but none have ever explained what the problem is and how they overcame it so I would take the claims with a pinch of salt!
Good used ones sell for huge prices on Ebay, so even at 250 quid a wheel you will be well in front.
If your wheel is true I would just have the hub water blasted or whatever and polish up the rims and spokes best you can, although the stock spokes are prone to breakage.