In reply to Flat4matt:
Short answer is you'll probably be fine.
Long answer:
The only bit that really matters here is the dimensions in pixels and the pixels per inch (ppi). dpi is really a printing term that gets misused.
You can print at anything between 180 ppi and 300 ppi and get acceptable quality, depending on what you accept. Magazine quality is around 250 dpi, with the nicest book printing being nearer 300. Below 200 you have the risk of pixelation being visible - jagged edges etc. You can use software to scale up the photo to get more pixels, but do too much and quality declines.
In my experience Photoshop generates a load of extra pixels when stitching anyway, so I avoid scaling them up further.
You starting with a big file so no problems there. The reason it is 'only' 15Mb is likely due to the fact it is a jpeg, which compresses the file size. Scenes with a lot of snow or blue sky can be compressed much more effectively than those full of ine detail.
Digital printing generally gives two options: inkjets (like your home printer but bigger) or lightjets, which expose traditional photographic paper by scanning laser. Lightjets rarely go much bigger than 24" wide so you'll be looking at inkjets.
Inkjets give you a range of paper choices - photo-type papers, canvas, or textured papers - usually cotton.
With lightjets or inkjets with photo papers you'll need 250ppi+, and you'll get a result like a traditional photo.
With textured papers or canvas you can get good results printing below 200 ppi, down to about 150 ppi. I've sold a few of my big panoramics printed at wide like this, and they look great. With big prints folk don't tend to get so close anyway.
I get lightjet prints done by peak imaging, and inkjet prints by Inframe in Sheffield. I'd try to find an inkjet printer you can visit and test print a portion of the print first. Prints rarely look identical to what you see on screen.