Identifying where which screws go where.

I recently purchased an iPhone 4 (Verizon) from someone who tried to replace the front screen. They decided it was more than they bargained for after they stripped most of the internal screws and put the phone back together.

When I opened it I noticed that the screws were either stripped or missing so I ordered replacement screws.

Because there are so many screws of different sizes etc. I couldn't figure out where some of them were suppose to go.

I segregated the screws in hopes of identifying by deduction what size the screws were as compared to the repair manual since it tells you what screws to remove and their size. However. I found this pretty hard to determine in some cases.

Is there a diagram or something that I can use to help with this issue?

Additionally, I'm not sure if the previous owner damaged the antennaes when he put it back together.

The phone has a very week wifi signal and 3G signal. How can I tell if they need replacing?