As above.

I have a option to replace a slightly to shot a CSU with a uncut NOS one for not a lot of money.

Easy at home task to do?

I’ve played with and serviced my own forks for years but never stripper out a CSU before.

For the purpose of the above we’ll leave cost and VFM out of it!

How’s it bonded what’s in the kit? How much does the csu and stanchions cost as one. Vfm is actually the biggest factor here

If you mean the entire CSU, as in moving internals and lowers onto a new set of uppers it’s barely more complicated than a lowers service.

– remove lowers as normal
– remove damper from top of one leg
– remove air/coil top cap and gubbins from top of other
– turn upside down and the depending on model of forks remove other end of damper and other end of spring respectively (socket set or circlip pliers required depending on model)
– re-assmeble in new uppers with correct fluids and replacing any seals/o-rings required.
– replace lower legs on new uppers with appropriate lube
– ride bicycle

Your main pitfalls are going to be if you have all the right tools and juices available. while forks don’t normally need any exotic tools they do often need ones in specific sizes that you may or may not have.

And as always, if you’re not confident then seek assistance in person or pay someone professional to do it.

Depends on make, but yes; if you have ever done a full service on a fork you most likely had a bare CSU in the stand at some point.

The actual swap is easy, but you need to potentially re-size the bushings in the lowers so they are not too loose or too tight on the upper legs, otherwise your NOS CSU could end up as KOS (knackered old stock) very quickly.
If they’re only a set of cheapo forks then go for it.
If decent forks then you probably want to get it done properly.
I had a similar dilemma with my Foats Floats and decided that, as they were good in every other way and I intended to keep them for a while that it was worth it.