Green Card for Sibling - I 130

[arvinder]

I am a US citizen and want to sponsor my sister, an Indian national, for a green card. I have done research online to understand the process. Could you please answer the following questions for me?

It appears I have to file form I-130. Since I live in Virginia, I should send it to the Chicago lockbox. I also see that there are multiple processing centers with varying processing times. For Virginia, the center is Vermont. 

1. Does the Chicago lockbox send the file to Vermont? 
2. Nevada and Texas have much shorter processing times. Is there any way my file could go there instead?
3. Is the priority date the date the file is received at Chicago, the date the file is received at Vermont, or the date it is finally approved?
4. Regardless of where the file is processed, is it correct that it will end up in the queue based on the priority date? (currently June 2004)
5. Finally, my niece and nephew (ages 7 and 9) will definitely age out based on current priority dates. I read about CSPA on some forums which looks like a way out. For this reason, is it better to process at Vermont vs. say Texas?

Many thanks,

Arvinder