Can a self-paced-reading & grammaticality judgment task be programmed in PsychPy or Open Sesame?
Disclaimer - I'm a big fan of, and occasional contributor to, OpenSesame. 


Yes, but you can't expect anyone here to do it for you. 
I would recommend using OpenSesame for this, as you'll need to use Python, and OpenSesame makes this side of things easier for beginners. 
My advice is to head over to the website, take a look at the documentation there, have a go yourself, and use the forum there to ask for help in specific points.

I will say though, that it's much better to attempt to design the experiment yourself and ask for help, rather than looking for someone to do it for you. The OpenSesame people really appreciate that!