New User - Upgrading from Aperture - willing to forgo all aperture meta data

Assuming I have never used this product, have the images stored on an external HD - where do I begin?  These are my constraints and thoughts:

1) I have to upgrade to Lightroom from Aperture

2) I have a large number of RAW images > 10,000

3) The Aperture library file could not handle all of my images - requiring me to create multiple library files by year for multiple years.

4) I would prefer to have 1 Catalog file for all images.

  4.1) Can Lightroom handle 10,000 - 50,000 or more images in a single catalog file - what are its limits?

5) I would assume the catalog file will be quite large - should I store it externally or locally on the computer?  Knowing remote storage  of this file will limit remote access.  What can I expect in terms of file size and probability of corruption with increased size of catalog file.

6) When traveling I will need to import images into a local catalog and store the images locally. Upon returning to my office I will need to:

  a) move the RAW original images to the RAID - how is this done?

  b) merge the temporary Catalog file with the master catalog file - how is this done?