Any idea how I can import my phone book from Nokia N70 into my Gmail account?
First, you are going to want to export your contacts from your N70 into either a comma-separated value (CSV) file or a vCard file. I don't have an N70, but a quick Google search turned up this freeware application that you can use to create vCards from your N70 contacts. As an N70 owner, you might already have tools that can do this, you can try to find one, or someone can point you in the right direction. If you want to ask around about tools, you can try the Electronic Gadgets Stack Exchange - I'm sure people there are familiar with the N70.
Once you have the vCard or CSV file, go to your Contacts and click the Import link. Upload the file and done.
There is an easyer way! if you go to http://memotoo.com and setup an account you can have your N70 contacts synced using one of the provided applications to that service. Then whenever you get a new phone you can sync your contacts over the air.
This service also supports syncing your contacts from Facebook, LinkedIn and most other contact, calander online stores so you have a single point of truth that can sync with your phone.
I like it as it supports pictures as well and you can check out how I set it up on my blog.