Two ways to do check if a SharePoint list exists (that I know of)…

1. Put it in a Try/Catch block

        /// <summary>
        /// Utility function to check if a list exists
        /// </summary>
        private static bool DoesListExist(SPWeb web, string listName)
        {
            try
            {
                SPList list = web.Lists[listName];
            }
            catch
            {
                return false;
            }
            return true;
        }

2. Use the TryGetList function from SPListCollection:

if (SPContext.Current.Site.RootWeb.Lists.TryGetList(ListName) != null)
{
     DoStuff();
}