You're not as thrilled with your site as you'd like to be and you don't have much money to spend. What makes a website a 'fixer upper' and when should you bite the bullet and start from scratch?

It's almost always a do-over.
Of course there are exceptions, but very few are valid. Think of it the same way you think of shopping for cars. By time you're starting to wonder if you need a new one, chances are you have already waited longer than you should have. Yes, it will suck to carry a car payment again, and yes you hate spending all that time researching, test driving, and haggling, but you know in the end you'll be thrilled.

It's a fixer-upper when:
You love the look and feel of your site. When someone asks you how to find something on it, you can instantly tell them where it is. The information is current and fresh, and the design looks like it could have just rolled out of the shop yesterday. You're not bored with it, and you still get rave reviews from site visitors (visitors = paying customers, not friends and relatives) about how it's easy to use and looks great. You really only need to adjust some existing text and photography.

Otherwise, here is why starting over just makes sense:
There was once an study that claimed that the average web browser decides whether a site is reliable in one-twentieth of a second. That's faster than an eye blink. Think about how many times have you been searching for something online and stumbled onto a site that looked sloppy or unpolished, and 'instantly' closed the browser, assuming it to be outdated or amateur. And you won't go back, and neither will the potential clients that stumble on yours.

If you are here, chances are your original website designer is nowhere to be found. With that in mind, it's likely going to take the 'new' designer just as long to pick through someone else's code as it would to just start over. Don't have the original design files for your site? Or the original fonts? Watch the billable hours climb as the new designer you hire spends hours trying to exactly duplicate the look and feel of your current site. Wouldn't you rather spend that time and money having them put together something fresh and new?

If your site has programming behind it that is proprietary or especially complicated, that is even more tricky. You wouldn't patch a rubber raft fifteen times, so why waste money plugging the holes in a leaky old site?

What to do if you insist on or are forced to keep what you have.
Track down your old designer or programmer. While the easiest thing to do is get them to make the updates for you, that might not always be possible. See if you can get your hands on the original site files, whether they are templates, layered PSD files, or even just the .ttf files of the fonts that are used. These will make it far easier for whomever is about to work on your site next. Keep in mind that not all designers are willing to pony up that sort of thing, but chances are if you have a good relationship with your designer, or are willing to pay a little extra, they'll pull the 'in case of design emergency' zip file together for you.

Just go for it.
Face it, new stuff is just exciting. It doesn't have to be state-of-the-art or cutting edge. A new coat of paint and some new sheets can make your bedroom feel totally different. Why not give your customers that same excitement by switching up the old site with something fresh and new?