I have a BIG Lightroom 3 Catalog stored on an external hard drive. I upgraded to Lightroom 5 last month, have experimented/familiarized myself with new version the last few weeks & am now ready to consolidate last few weeks work with master catalog, aka upgrade the master catalog. Anything i should be worried about/ aware of before I do this?... Lots of work in the old catalog, don't want to make any mistakes.
No, I can't think of anything you should be worried about if you are going to do things the right way. In Lightroom 5, select File->Import from Another Catalog and then point to the LR 3 catalog. Should go smoothly (although it might take a while depending on how big BIG is). Make sure you make backups of both catalog files before you start.
1.5 TB of photo files ("Capture folder"), 200 GB Lightroom 3 folder.
Watching this video first helped calm some of my pre-upgrade jitters... How to Upgrade to Lightroom 5 | Laura Shoe's Lightroom Training, Tutorials and Tips
(I'd already read the help text in the Adobe Lightroom catalog FAQ )
Here it goes though! :-)