Congratulations!! Girls are great. I had to go back for a re-scan with my 4th dd because they couldn't see the heart well either. Just beware that they will take an insane # of pictures when you go back. It freaked me out that they took so many, but that's what they are suppose to do, so don't let it get you nervous.
As for having a second....if it happens that will hopefully be cheaper since I have loads of girls stuff. Boys get into expensive pastimes too so I'm not sure either sex will save you from that!