The siding does need to be washed before you paint as the dirt and mildew need to be removed. If the siding is delicate then you can wash it with a product called JOMAX, which can be done with a pump up garden sprayer and a garden hose. You will need to scrape or sand to remove loose and flaking paint to insure a good paint job and don't worry about knocking some of the texture off the siding as it should not be that noticeable.

If there are more than a few spots that are bare wood after scraping and sanding then I would prime the entire surface. In your area there will be a Sherwin Williams store and they have a great exterior acrylic solid satin call Woodscapes and they will give you correct system to prime and finish you siding. Most paint jobs last 5 to 7 years (sometimes more) but remember if the existing coating lets go everything on top of it will peel to.

Hope this helps out.

Thanks so much for helping with this! I've read about this woodscapes product and will definitely check it out. Your advice is great and if I get 5-7 years from this paint/stain job then I'll be satisfied!

Thanks again.

Polly