Transferring iPhoto Library from 10.3 to 10.8

Question

My folks recently upgraded from an eMac running 10.3 / Whatever Cat to an iMac running 10.8 / Mountain Lion.  I have transferred the old iPhoto Library to the new computer, and renamed it slightly (but did not replace or throw away the new iPhoto Library that came with the iMac.)  That new library has nothing in it.  I have downloaded and used the iPhoto Upgrader but have not yet done the part where it updates the photos for hours when you open the library with iPhoto itself. 
Apparently in iPhoto 11 you could just keep two libraries forever, but this is not desirable in my parents' case.  So my questions are: 
1) do I want to import the old library or simply replace / throw away the new library by putting the old one in the Pictures folder?  (It used to be that importing an old library folder was a bad idea, is that still the case?)
B)  if I replace the new iPhoto Library folder, will iPhoto store photos in a slightly odd way? For example,  when I upgraded to a small MBP after my first Macbook died I transferred my old iTunes library.  But because of that, all my music is actually stored in the "Music" file under "iTunes Media" and nothing is actually in the "iTunes Music" folder.  Not a problem really, but not all that clean either. 
3) in either case, will the dates of the photos remain as they are?
I'm know other people have similar questions, but most of the time they're transferring from a more recent version of iPhoto, so I just want to be sure before trying anything.  The photos are backed up elsewhere, so no pressure. 
I appreciate the advice. 

Answer 1

1. Throw away the new empty Library and put the transferred one into the PIctures Folder. Then Hold down the option (or alt) key key and launch iPhoto. From the resulting menu select 'Choose Library'
NOTE: there is no importing involved here. Just moving into place and starting iPhoto.
2. What does "slightly odd" mean? Note that there are changes between iPhoto 08 and later, and iPhoto 1 and 6, in particular how the files are accessed. For help accessing your photos in iPhoto see this user tip:
https://discussions.apple.com/docs/DOC-4491
3. Yes.