siva-
You can certainly implement your own solution via custom Javascript and CSS.  However, for the time you'd spend creating and testing your own solution you'd probably do just as well to spend $30 for one of two existing DNN modules.
 
Option #1:  More Than ToolTip
The first option is the "More Than Tooltip" module from Mandeeps.  It not only provides standard text tooltips but also allows you to include entire modules (any module) as a tooltip.  for instance, you could play a video in your tooltip or use a Survey or Feedback module as your tooltip.

The module extends tooltip ability to any module that allows you to define HTML so it's not limited to just the Text/HTML module.  You could easily add tooltips to XMOD forms, for instance.  The module also provides 25 different tooltip rendering options so you should be able to find an option that works well for your needs.
 
NOTE: I do not know if the module works for DNN 5.x (it should work but I've not seen confirmation on this).
 
 
Option #2: OnyakTech module "Soma Elite"
Another interesting option for only $30 is the Soma Elite module from OnyakTech.  This module is a bit more automated in that you can declare a certain word to have a tooltip and the Soma module will add the tooltip to all occurances of that word.  It also has options for highlighting any designated words so you know which ones have tooltips.  It includes other features like "automated" tooltips for links (you don't have to do anything to add link tooltips), Wikipedia lookups, email link tooltips, etc.

 
Cheers!
-mamlin