Hi Brooke,
I'm very sorry for your loss, it's awful to lose a pregnancy.
When you go back tomorrow for your second HCG test, the nurse should talk you through everything, so make sure you take these questions to her - and ask your partner to ask them if you find yourself too upset to do it.
If the miscarriage is confirmed, you may continue to bleed for a while and you should use pads, not tampons while you're bleeding, and no sex until all the bleeding and discharge has finished for a while.
You can start to ttc again when you feel ready, you don't need to wait for a period but if you decide not to wait then do at least make sure you do some pregnancy tests before starting again. You need to see a -ve test (sorry, I know you don't WANT to see that) so you can be sure that if you do get pg quickly, then the +ve test is real, not left-over HCG from the previous pg.
There shouldn't be any complications from the miscarriage - things to watch out for are signs of infection (temperature, feeling 'fluey, smelly discharge, discomfort). It can take a while for your period to come back, but if you are worried that it's taking too long (say 8 weeks?) then talk to your GP.
The risk of having a second miscarriage after you've had just one is the same as any other woman who hasn't had one - so basically, you have as much risk or chance of failure or success in your next pregnancy as anyone else. The sad thing about having experienced a miscarriage is that you will probably experience more anxiety in your next pregnancy than other women.
Don't give up, it's a horrible thing that's happened but it's not necessarily a prediction for your future plans for children. However, do take time to acknowledge and grief for what you've lost.