You can do it cheap, and cheap is what you will get.
I would consider doing nothing, until you find out if you want to keep the 9N. The reason being, if you throw a cheap paint job at it, and then want to sell it, the buyer who might want to restore it will (may) look negatively at having to also remove the cheap paint. Or he will wonder what it is that you are trying to cover up. I would rather buy something that doesn't have a "pretty" cover-up, kind of like make-up on a woman. Have to guess at what lies beneath. But that is another subject. (Maybe itsmecindi will get a story out of it /forums/images/graemlins/grin.gif)
If you decide this is the tractor you want to live with for awhile, and you would rather have the cheap paint, then go for it. It is yours to do with what you want. I found out with an older Deere (420) that once I removed the oil and grease, the John Deere paint covered quite well (a bit of wire brushing on some non-painted rust spots helped). Albeit that was when lead paint could be purchased, and it can't be beat.
But there are good paints to put on and really not that expensive compared to the hours invested preparing the tractor and putting on the paint (IMO).