What reputabel business can replace my iMac HDD?

The HDD in my 27" iMac is bad, and needs to be replaced. I've used Best Buy/Geek Squad in the past for issues like this, but they said their policy has changed, and they no longer perform the repairs in shop, but instead send the computer out which takes 2 - 3 weeks. I'm not comfortable with that. Does anyone know any other reputable business that can replace a Mac HDD in shop? and what guarantee does the consumer have that personal information won't be stolen from the hard drive, such as passwords and such? I'm in the central Jersey area. Thanks in advance