Pregnancy She is Pregnant...when is she due?

So when i got my guinea pig Marmalade, I asked the person if she had ever been bred or with a male and the person i got her from said she was pregnant when she was young (part of a 4H program). Since then she has not been pregnant or with a male. After about 3 days, i noticed she was gaining weight and i asked again if she was with a male at all. she told me that Marmalade was with a male at the end of december. I can definently feel little lumps and can feel them move. I asked again about how long Marmalade was with the male and she told me from end of october to end of december, but she never saw them breeding.

My Marvolus Marmalade is definantly pregnant. I can differentiate the babies (feel heads and bodies) and feel them moving. How soon after this part should i expect babies? What does labor look like in guinea pigs? If this was a dog or a cat I would have no problem, but i feel a little out of my element with my magnificent Marmalade (obviously I adore her, and am terrified to lose her). Any and all info is appreciated!