Hey people! Need some help again!

I am trying to use the MS without any data plan at the moment, only relying on Wifi. The problem is, I can't seem to download any apps from the Market through Wifi, my downloads will state that its starting and it would take ages and it never starts! The wifi port is just in my room.
Is it normal to wait quite long?
Or would I need a data plan to download apps?
Or can I download it to my computer and transfer it to my MS?

Another problem I am facing is my credit is being drained!
I am currently using:
Settings>Wireless & Networks>Mobile networks>Use only 2G networks
There is a icon with a letter 'G' at the top next to the battery.
Is that causing me to lose my credit?
What can i do to avoid losing credit? I wanna only use Wifi if possible.

Updating can settle the alarm bug? Just go to settings>about phone>system updates?

Please and thank you!