reseting pin code without remote or old pin

I bought a house 2 years ago without asking the previous owner the code to the garage door opener. I delayed long enough that I have now lost both remotes, and still not knowing the pin to open the garage from outside. I have marantec 4700 garage door. 

I spent a couple hours online, but can't seem to find answer. I still have access to the garage door brain (or main unit box. not sure what you call it) from inside the house. My questions are:
- Now that I have lost both remote, can i simply buy a new remote and reprogram it without the old remote? I cant seem to find instruction online to do that. they all require old remote.

- where would be the best place to buy the remote? I don't even know what frequency they run on. From my research online, they seem to run on different frequency. 

- is it possible to reset the pin outside to open the garage door ?

I know this is stupid. but now i need to go through the main door, press the main unit of the garage door to open the garage from inside, and then press the button on the unit again to close the garage door.