Do you have any sales experience? If not, knowing computers well can be sufficient if you are good at communicating with clients to learn their needs and make smart suggestions.
The best salespeople get to know the client, asking the right questions then listening closely. If a PC customer believes you are interested in them and their needs, you may have a client for life.
Dress sharply, smile and assure them you are an active daily member at the top tech help forums on the web.
You can always pose the questions of your clients here to get added expertise. I do this and amaze mine at the wealth of information to be had, often in real time.