Is it possible to renew my Indian passport online by myself or do I?
The only way an agent or a shop can help you is in filling the application form in case you cannot use a computer. If you know how to use a computer/smartphone and have access to internet, which you seem to have as you have posted this question here, you don't need any agent. You need to fill the form online, pay the fee, book an appointment at a convenient Passport Seva Kendra to complete the application. The process with the required documents is clearly explained at the passport application website and you just need to follow the instructions.