You are just getting started. You should already know your BLS skills. Learn where everything is on the unit. Assisting with the advanced procedures will come with time.
Man, if you're going to last in this job field you are going to need a supportive girlfriend/wife. You need someone to be understanding. Sounds like this isn't the one.
I would take as much time as you think you need. If you feel you are prepared, take it right away. If you think you need some time to study, take that time. I waited about a month and a half after the class was over to take the test.
From what I understand the only difference between the two courses is the AEMT has more emphasis on medical emergencies. Still the same skills though. But here in Houston there are many private organizations that offer EMT-B to Paramedic courses.
The best thing you can do is read! Read a chapter ahead of the next lecture so you are familiar with the content. Also, don't be afraid to ask questions if you are unsure.