1, The force due to gravity on the electron is its weight. I'm sure that you can work that out.
2. The force due to the electric field can be got by first working out the electric field strength (using the expression for electric field strength between parallel plates), and then using the definition of electric field strength in terms of force and charge.
3. Combine the above results to find the resultant force on the electron (you should notice something here that makes this very easy, in terms of the numbers you actually want to use). You can not work out the acceleration of the electron using a very fundamental relationship.
4. This is effectively a projectile motion problem.
I need to brush up on electric potential myself before carrying on!