Marketo Integration with Salesforce.com

Hello All,

I am working with my client and we are looking to integrate their live instance of Marketo to a vanilla Sandbox (eventual Production) Salesforce.com environment. I have a few questions for the integration and would love the help:

1. The configuration to my Sandbox Salesforce.com with Marketo should be pretty straight forward? I've been hearing that by doing so, it might wipe all of the data in Marketo??!?!
2. How have you guys dealt with your Anonymous Leads? Is it possible to push to Salesforce and maintain from there? From my understanding, there is a "limit" on the amount of Leads you can have in Marketo, so these Anonymous Leads can add up pretty quickly.

Thanks!
Phong