There are some other tools than SurveyMonkey. You can also explore some of the temp field options people suggest here on the forums. Please do a search for surveys in marketo.
But if you aren't technical, it is worth paying for a solution. It will save you a lot of headaches.
SurveyMonkey is definitely worth the investment, you should really try to make a business case for that tool as it has a fantastic out of box integration with Marketo. You are going to get ramped up faster and have much better results with that tool in particular as the integration is ready to go.
The hard point is that they are charging very high the integration to Marketo. You will buy your licence 900€ a year, but the Marketo Integration will cost 8000€ a year!
So it's only worth it if you have the volume and you really have the usage of the info that is pushed back to Marketo.
Last point (we installed it a couple of weeks ago) : the integration is now using custom activities (which has to be activated by support and is not GA), which is good in most of the cases, but, unless I missed something, no longer offer the possibility to map a Marketo field to directly save the result of one question.