I made an order a while back, let's see what it was...
So we've got a 1/100 box, 2 HG's, a decal sheet, and maybe 1 or 2 thin boxes with extra parts. This order rounded out to about $95 USD before shipping.
Now, if you're in the United States, you should have shipping options that look like this.
For this order, I went with International Shipping, and it arrived in about 3 days (from Japan to the East Coast!). This shipping was about $45 iirc, and that was for 6 items, three of which are full kits and three of which are dirt cheap to ship. Given that you want two kits, I'd expect it to round out to about $30 for even remotely fast shipping. If I were you, I'd recommend waiting to buy more kits from HLJ. They have awesome prices if you're buying in bulk, but only a couple items isn't going to save much money.
You should be able to just glue the part back on, since the breakage point isn't mangled at all.
I've got a Gundam Discord chat if you're interested