craftgrrl | Help with painting

I've been lurking here for a bit but now that I've moved I have a lot more space for crafts and a brand new apartment to decorate. The first step is going to be painting my "office" (the second part of our living room) a light purple, with dark purple trim (around the windows). I've bought a second hand Ikea desk that's made of pressboard (or "chips" as they call it) - it feels like plastic, but it's stained (coffee rings and the like). I want to paint over it (to match the trim), but I'm not sure it's going to take the paint the way it is. There was a post on here or on

saucydwellings where someone wanted to paint over a dresser like this and there was some debate as to how to do it. Was the final answer to sand (if so what grade) and then use primer? Can I just use primer (and if so what brand)? Will the same latex paint we're using on trim be okay on the desk once it's been primed?
If someone can link me to the original post as well that would be great. I dug through the memories and a couple of weeks of archives but came up blank.
Thanks!

x-posted to

saucydwellings