most parts stores have a loan a tool program. However to do any work on a car you'll need to start building your set. I good set of sockets short and deep shouldn't take too much room and will allow you to do most jobs. Even if you bought cheaper harbor freight stuff, it's usually good for the little amount of hell you'll put them through.
You can also have your alt tested at those stores before you go to the trouble of replacing it. same goes for the battery. But first check the obvious with the connections to the battery in the trunk.
assuming you bought it private party and not a dealer, which would include some limited warranty?
2009.5 G8GT Premium OnyxRed Interior
corsa catback, vararam intake, cortex tune
custom audio, sharksfin, HIDs, LED Fogs, 20" MRR GT1's, Kayhan headunit