Re: This is a good idea
You're confusing booster rockets with simple low impulse thrusters.
Once you escape atmospheric drag and the extremely high impulse needed to overcome it, the vast majority of motors use simple hypergolics (and some used simple pressurised cold gas)
As others have said, almost all satellites have accessible fuelling ports, because they had to be filled up before launch. The hard part is connecting to them in a "weightless" environment without the things simply bouncing off, which means not only to you have to fly up to the bird, you actually have to hold onto it whilst you plug in - and with the antenna/solar panels deployed that can be a pretty delicate manouvure if you want to do it without breaking parts off given the delicacy of parts and inertias involved.
http://www.esa.int/spaceinimages/Images/2012/09/Galileo_FM3_Fuelling3
If you're ever in London, there's an Intelsat with half its antenna deployed on display in the science museum (the other is furled). Think of a butterfly and the fragility of its wings and you won't be too far off.
Biting the hand that feeds IT
