Well J., that is one sweet boat you have. Congratulations, and welcome! I have a '79 Oday 23 too, and have done quite a bit of work on her over the years. I would be happy to answer any and all questions you have as they come up, and you will find that there are a lot others who participate here with a wealth of knowledge too.
Your specific questions: It's easy to paint the bottom of the 23. You can do it yourself if you are so inclined as it is no different than painting the walls of your house. The one difference is the prep work. Whatever paint you have on there now should give you a relatively smooth surface to coat. Sometimes bottom paint comes off unevenly, exposing undercoats of paint or even the bare hull in some places. In such instances, you should try and sand the areas so that the new paint can go on smoothly. The sanding dust is toxic, so you need to wear a mask and cover yourself up (including your face) as much as possible so you don't wind up looking like Papa Smurf. A sander with a dust collection attachment is a must.
There are two types of bottom paint: hard paint, and ablative. Hard paints leach their biocide through the exposed area throughout the season, but once they are taken out of the water or after several months, they "wear out" and are no longer effective. Like their name indicates, they do not wear off, and successive coats of them over the years build up. Eventually, they will have to be sanded off (especially if you like to race) in order to get a surface that will take another coat of paint. Sanding off years of paint is a big, messy job. Hard shell paints are the least expensive option.
I like to use ablative paint; it wears off as the year goes on, exposing fresh biocide. The fact that the paint wears off also eliminates the need to completely sand down the bottom every few years. And, ablative paints come in "multi-season" formats. This means that the paint will stay effective for multiple seasons; no need to repaint every year. The multi-season ablative paints cost about twice as much as hard shell paint. Worth every penny if you ask me.
For the Oday 23, it takes about 3/4 of a gallon to put on one coat of ablative paint. I bought two different colors the first time I painted the bottom of the boat. I put on a coat of red, then covered that with blue. Now, when I see red paint peeking through the blue, I know where the paints needs a touch up. I buy a gallon of ablative multi-season paint every few years. I use West Marine CPP or the Interlux Micron CSC, whichever is cheaper during the spring sales. I have gotten four years worth of protection from both. I still have the same base coat of ablative paint from 11 years ago. The West is usually on sale early in the spring for around $120 gallon, the Micron is usually more. A friend of mine tried the new water based, non-copper paint, but said it didn't work very well and went back to the Interlux.
As for the painting itself, just get a pan and some rough rollers, and you are in business. One thing I recommend: get one of those paint stirrer drill attachments. It makes life a lot easier. I use mine only for bottom paint; in fact, I have a lot of painting equipment that I don't even try to clean that I save only for bottom painting: a roller tray, rollers and a tyvek painting suit. Get yourself one of those packs of latex gloves too, and a bunch of disposable dropcloths. Designate some rags that you won't mind throwing away. And don't even think about brushes; stock up on the disposable foam ones. They are great for painting the inside of the centerboard slot and doing touch ups when you don't need the whole roller thing.
I find that it takes me about two hours to put one coat of bottom paint on the boat; that includes set up, painting and break down. If I have help, it takes much less time than that.
Hope that is helpful. Welcome again.
