CPU & RAM Upgrade options

Hi all,

I have a dell insppiron 1525 laptop with 2 GB RAM & CPU of Intel Core 2 DUO T6400.

I want to add 2 GB more RAM to make it 4GB. Is it possible. What constraints I need to take care of? Please recommend few good RAM options for the said purpose.

I also want to upgrade my CPU. What compatible Intel CPUs can I replace with ? Please recommend 3-4 good choices.