Cap exempt to cap subject H1b

[Physio_W]

Hi I am currently on H4 and have an employer(staffing agency which partners with a research organization) ready to sponsor non cap H1b right now and then in April 2015 file cap h1b. My question is 1) if and when I have to go for stamping will there be problems?
2) any suggestions who has transferred from Non cap H1b to cap H1b, anything that I have to be aware of?