Be absolutely sure you want to be a tester before you make that switch. After a few years away from software development it will be extremely difficult to go back. It would be like working in software maintenance with some legacy language/technology for years and then trying to get a dev role using the latest stuff (actually, it would be worse than that).
In regards to your second question - yes, after doing testing for a while, you will be considered a Test Engineer (or some equivalent title). In other words, yes, this is a career change, you would be leaving software development to become a tester.
Now, testing isn't a dead end -- at companies I've worked for testers can become leads of a test team (esp. on large programs), QA manager, etc.
Personally I wouldn't do it, but I have known Software developers that transitioned to 'Test Engineer' and loved it. I've also met one that tried it for a few months and then ran away screaming. It probably depends on your personality and what type of work suits you.
A good tester is a great resource to have, as much as I may get frustrated with them :) If you love writing and/or following processes/procedures, are extremely detail-oriented, and enjoy making devs angry, then testing might be for you.