The advantages of using an agent are exposure to thousands of qualified buyers, which produces a better financial return and speed of sale. If you have done it 3 times I have no doubt you could do it again, clearly you are satisfied with previous results. I find most FSBO have no time limitations and are willing to keep home in market for long periods just to save a few thousand dollars, if that works for you then best wishes for a speedy sale.
You can sell a home in any economy. The question is are you willing and able to set a price that will result in a sale. Renting is an option but ask yourself are you ready to be a landlord; will I have a positive cash flow; what will my carrying costs really be (be mindful to calculate your property taxes which may increase when it is no longer your homestead); how will the property being a rental effect the insurance premium I pay; and if you are looking to buy another home, will I qualify for a second mortgage.
As for fixing up the home, I would fix the roof and the front yard. Curb appeal makes a huge statement to any buyer. And the roof, every buyer I have ever worked with or shown a home to asks the same question, "How old is the roof?".
If you decide to sell I wish you the best of luck.