Other than installing the NIC mentioned above, you shouldn't need any additional hardware. Although, if you start to use the DSL line to view video on demand or other memory and processor hungry functions you may well decide your PC is too slow. Yes, you certainly can. However, there are several software programs that make this a simple task. Some additional hardware will be needed, such as a Ethernet hub, and additional NIC's.
Installation time varies.
Once you have been qualified, you will be contacted to set up an appointment to have your DSL line installed. This is generally anywhere from 30-60 days. SDSL however, is geared better towards businesses since it does use a DSL router rather than a DSL modem. This will allow you to better protect your business, and it's data. However, there are costs to doing so.