Urgent Response requested: Autogrow of SQL DB

I'm referencing this post:

http://community.spiceworks.com/topic/21106-autogrow-of-database-file-cancelled-or-timed-out-error-m...

My SQL DB has grown very large (DB file is 2GBs while the Log file is 450GB... yes, you read that right).

I've implemented the change in the mentioned post (changing from 10% to 100MB growth) and SQL Manager is "executing" it.

I need to know if this operation going to take a long time (450GBs).  It is impacting our business and I need to make decisions based on what's happening.

Thanks in advance