I might suggest that you use
Simplify Media (AppStore) that allows you to view many other people's libraries, and you could use SwapTunes as well. Now, if you want to maintain your device on your computer, you could jailbreak on their computer, deactivate the device from their account, then activate it on yours, then you'd have a jailbroken device that works with your computer.\
Also, this is the correct section for your question. Now, how come you don't have the space for a 25 MB application and 250 MB firmware?