mating and food

Question
 On sunday I just recently bought a male guinea pig from the pet store and by the end of the week with get a female guinea pig.  Well I really have two questions.  If I put two guinea pigs of the opposite sex in the same pen, should I be aware of anything? If I would like them to make "little" guinea pigs is there anything I should know to help them along the path? and Are there certain foods I should be aware of not to give them, because right now I'm using pet store food but If I'd maybe want to give them vegetables if there may be something that I should be aware of? Okay that was three but I don't want to endanger them in any way, thank you for your time.

Answer
Ok, first I must say that I strongly discourage breeding for fun!

I will help you, but you should know that breeding is VERY dangerous to the sow! If she is over 1 year old, she will  probably die! There is nothing you can do to "help",they will do what needs done, when you notice her gettting bigger, you need to get him away from her ASAP! They should have veggies and fruits daily, breeding or not...they should also have pellets, fruits, veggies, hay, and water unlimited throughout the day! Please take care of the babies, be sure they go to good homes...IF you would look around, you would be shocked at the ever increasing number of guinea pigs in the shelter and in rescues...
Please do not breed just for fun! IT is dangerous to the mother!