Hi Daffy, hit F8 on the keyboard to switch between Object and Component mode OR you can right click on an object and choose component selections like vertices,faces or edges then simply select or drag a selection in the Persp view and push and pull all you like.
If you want to create a presized /prescalled object, when you go to the create polygon menu click on the little box next to the primitive of your choice to go to it's optionsand put your numbers in there and every primitive you create will have those values until you change it or reset it.
The tutorial movies that come with Maya would explain these basic things, Did you not watch them ?

Hope this helps a little anyway and btw F1 on the keyboard brings up the Maya help files.