With the upcomming release of Service desk 7, sept 4th, I really would not do any customizations for the old Help Desk. Just keep it up and running and start planning for a transition to Service Desk 7.

I think what you'll want to do is add static fields.  Once a contact is selected the new incident screen should refresh and display that information.  It will work similar to the way the VIP flag does. 

I can't test right now as my Test helpdesk server is also a Test Asset server and we've got some training on Asset going right now. 

With Service Desk 7 comming out I wouldn't abandon all customizations.  I know I'm not jumping to it right away and many others won't either if for nothing other than budgetary constraints.  Maybe first quarter of next year I might be able to do something, but it depend on my server team and what they have hidden away in the Data Center. 

Fine,

I think I'm going to postpone it till the next release. I know it was planned to be release lately last month but it has not till now.

I tried to search for any documentations or guides for upgrade to Service Desk 7 and customization guides, but could not find anything.

Do you know where I can get these guides at least to prepare for the upgrade and customization process.

Regards,
Mustafa

Since Service Desk 7 is built on Workflow Solution you might start by looking for information on that.  I've not seen anything specific on Service Desk just yet.