I know not to grow garlic in the same bed as the previous year, however last year I planted it in a raised bed with bagged soil and homemade compost. If I replace the soil and compost, can I use the same raised bed? Also, is bagged potting soil good for this or should I use some other king (topsoil, etc.).?
It is always a good idea to rotate your crops to prevent disease and insect issues. However, if you have a small garden this is not always possible. If you had issues last season with disease such as white rot, work in a lot of compost to infected beds and don't plant allium family members for 4-5 years.
If you did not have disease issues, you do not have to replace the soil. Work in some organic matter like homemade compost or you can purchase compost by the bag, for example Leafgro, composted leaves. See our website for sources of organic matter http://extension.umd.edu/hgic/topics/prepare-your-soil