How quickly can I deploy web based CRM software?

Depending upon your requirements you can deploy your new web based crm solution within a few days. It all depends upon the amount of customisation required and if you already have your business requirements mapped out without any integration into legacy systems it should be within a few days. 

How expensive is online CRM?

There are numerous products available. Prices range from around $50 - $180 per month. In order to really evaluate the price make sure that you have your business requirements defined and then find a vendor that provides most of the functionality as a standard out of the box product. For example, Outlook integration to allow syncing your CRM details with your Outlook contact, calendars and tasks are free in some products but others charge for the plugin.

How much can be customised by end users and how much requires technical IT staff?

Most web based CRM solutions allow end users to customise the application without intervention from IT staff. When integration to other systems are required the IT staff will be involved to design and build the Web Services integration.