There is no special Comodo "renewal" process if you have purchased a certificate in the past. You always have to request a new certificate, it can't be "renewed". Login to the Comodo ordering system and place a new order using the same company information and Comodo should speed up the validation process. Be sure to quote your previous order number in any correspondence with them.

The discount for Lindersoft customers with a current SetupBuilder subscription is 60% when you buy a 3-year code-sign certificate ($200 instead of $500).

Hope this helps.