Ya it was apparently going to happen in 1808 and was only canceled when napoleon backstabbed spain, Wellington had to apologize personally and Miranda had to look to the United states for support sense spain was now Britains ally. Not that I suspect the expedition would have done well, as miranda showed later there gust wasn't much enthusiasm for independence in Venezuela at the time but it would have been better then what he did historically (not that's a very high bar to clear) most likely a few forts taken before Wellington and his army falls to yellow fever.
Also not much to find on it sense it dint end up happening unfortunately.
Did Spain have any naval forces in the Americas or the Pacific during this period? At the very least, there seems to have been a squadron of some strength (albeit in disrepair) based at Cavite during the Second Coalition War, but what about the Americas? Was the entire Spanish fleet, more or less, in European waters?