Moving the documents will be easy via floppy, ZIP, CD, etc. You could even
place the entire win3.1 hard drive inside a USB enclosure and access it that
way. You might be able to attach the old drive as a slave inside the new
PC, but that can sometimes be tricky.
But, the real question you should ask is whether any XP-compatible program
can read the files, and if yes, will that program preserve the file format,
or distort things a bit. I recall that going from WordPerfect for Win3.1 to
Office 95 for NT a lot of formatting was lot. And, going from Office 95 to
Office 97 that some formatting was lost.