I've just done a couple trades since i'm new too, it was hard to work out how to do it but I got there.
Himeji would cost you anything between 500 - 800 FP's, It just depends on the seller but because Himeji is new, the goods are popular and it also depends which world your in, harder to get in some worlds than others.
I think most sellers don't require you to pump in all the FP's at once, so over a week maybe you can add fp's as they come, saves you using up fp packs in your inventory.
You just add the fp's to the GB the seller wants you too, usually their arc or whatever their levelling at the time.
Once your done adding all the fp's, you then create a goods trade list, you can use any goods you have the most of, iron age goods might be best, so for instance, one type of good required for HC is 500 nanites, so you would put up say 250 cloth for 500 nanites and so on for all 5 goods, you to put at least 2:1 goods up so the trade can work, 250 for 500, 225 for 450 etc.
Once you have set your goods trades you then message the seller and link all the goods trades you created, the seller simply clicks on the 5 trades to accept and you've got your HC goods in your inventory ready to.
I found I needed to trade down higher age goods so I could have enough goods in iron age to cover the 5 trades, so it's a good idea to get onto that process right away, have your trade goods ready to go.