Crutchfield will give you what you need to install. There's little risk of blowng the speakers on just head unit power (roughly 19 watts rms, even factory speakers can handle 25 watts rms).=, unless the speakers were already damaged somehow.
If you buy speakers from crutchfield they will give you any necessary speaker wires as well. So the oem speakers use a white clip to connect tot he factory wiring, they will give you an adapter to connect new speakers. You can get the 5.25" bracket from nalinmfg.com or ebay.
iPhone app user; excuse typos...thanx.