Questions and opinions of a Cable line with a back-up T1

My company currently has only a Covad T1 that connects the main office to the internet. This line is mainly for our billing office (located across the state) to connect to us for our Terminal Server. Our future plans for our main office include having a company E-Mail Server as well as a Web Site for employee access, applications, information, PR, etc. Our normal day to day internet access doesn't include much besides a GPS program(which gets replaced by google maps if it goes down, which it does a lot), various people in the office using their personal(professional) email, streaming music, typical office business use with nothing too critical relying on the actual internet and a majority of our connections are for internal use. With our future plans in mind my question breaks down to some parts.

• What are the steps (after figuring out who we're going with, what package, etc) in order to get a cable line working with a T1 in order to have the T1 as a back-up. I have done some research and either I'm more terrible at searching than I thought or there is no concrete documentation on this.

• What kind of bandwidth should I spec out or expect to get by adding in these features in the future for our business. I don't expect facebook level traffic but we do have a huge contract with the local hospitals (we do all of their medical transport) and the company is well known in the area so I'm not quite sure what to expect as it will mostly be local (by local think NJ, PA, DE, I expect nothing should be coming from beyond that area)

• And also, who do you think has the best support or way of going about this process and keeping a reliable cable connection working? But also allows a back-up T1 to kick in should anything go wrong. Options here include Comcast, Verizon, and a few local companies that probably just work off of them.

I should also add that the only guaranteed time the company needs to be connected to the internet is for our billing office which is between 8A-4:30P M-F so this is more for convenience than anything (downloading updates is a nightmare on the network, even during off-hours) and nightly downtime on the cable line is a non-issue.