Yes, just give it a good sanding down first. Use an undercoat first. The top coat could be a 'one coat paint' but it may not cover properly on it's own. It's what I've done in the past covering dark colours and it's worked fine.
Good luck
Depends why your painting it. If your doing it to help sell a house then the benefit of doing it properly are less (i.e. it will last a long time). If your doing it for your own benefit then no sand first, then undercoat.
MrsCheeks...that's not fair! If you're refering to one-coat paint, even the tin says, and I quote from the tin, 'A second coat may be require over dark colours'
Caroline2235, just re-read my answer and I should have said was;
Sand it down
Put on undercoat
Put on top coat
Hope this clarifies it for MrsCheeks too!