It totally depends on how small the seedling is. Seedling as a term can mean anything from just out of flask up to not quite near blooming size (NBS).
The smaller the critter, the less light and fert it will want. Basically you have to wean the young 'uns up to their adult dosages of light and fert.
If it's a smaller seedling, it's probably fine in whatever material it's already potted (note caveat about to follow!) The little guys haven't likely been in anything long enough to exhaust the medium. The rather big caveat is that the potting medium needs to be suited to your conditions.
The good news is that Dens like to dry out between waterings, and tend to be well suited to more open mixes, or mounting. If you're in a very cold (ie, dry) place in the winter, you might want to wrap bare roots in sheet moss or sphagnum moss. (Sheet moss is easier to deal with when wrapping mounted plants, even though it doesn't have the moisture retention of long-fiber New Zealand sphagnum.)
If you're not sure, post a photo when the tyke arrives and we can advise you further. Good luck with the new baby!