well the ram and the processors are built onto the board cuz its cheaper so unless you get the right parts and have super mad cow soldering skills then no those are not possible. and even if you did get them in there's a chance that the firmware of the ds wouldn't be able to use them.
So no i wouldn't recommend even attempting to try this cuz then your just wasting a good DS.
as for the wifi antenna. extra metal on the antenna may help but not much.
i'll Google the CPU Speed of the DS. i should find something...
here you go: Copied from
www.toptenreviews.com(Performance:
There’s a lot going on with the Nintendo DSi so it’s a good thing that the brains upgraded to meet the new demands. Processor speed has been doubled, compared to the DS, to
133MHz and RAM is up to 16MB, four times that of its predecessor. You might think that would result in remarkably snappier performance but in practice it just keeps up with the added capabilities. There are 256MB if on board storage which can be upgraded with up to a 2GB Micro SD card or a 32GB SDHC card.)