what tmobile plan should i get for my sidekick ?

I think you should get the unlimited texting plan, especially since you have a sidekick, and it would allow you to text very fast. It is only $20 a month for the whole family. Trust me I use like 100 texts everyday and you can go overboard with your 400 text plan if ppl text you. So unlimited is the best plan. I'm pretty sure that aim is part of the texting plan because last night, my sister and I tried out the email on her phone. It said that standard text messaging rates apply for sending out emails, so it must be the same for aim. Plus, we don't have Internet on our phones and it showed my sister's email. Btw, I'm 13, if you were wondering.
But if you want to text and aim, the unlimited texting plan is probably the best deal.

AIM is under text messging. when i had Yahoo IM on my phone it would use my text messages. and i like to text and IM people.