bbthefe,
Seeing that you are already experienced and hold B1 (I assume that's airframe & turbine engines? If you have piston engines & have a PPL, all the better), I suggest the following:
1. Study for the 3 written exams (General, A/F, P/P) on your own. All you need is the latest ASA Prepware books, it has all the questions and answers (MCQ). Then when you are ready, head off to US and sit for the 3 written exams in 1 go. You should be able to pass them with no problems.
2. Only go to the school for the "Oral & practical" preparation and then the actual oral & pratical exam.
Following the 2 steps above, you save $$$ on the written exam part. You do it at your own time. The written exam takes a lot of memorizing & little bit of understanding.
For step 2, I find that it is a must to attend the O&P prep. This is because the school will have all the practical stuff that you must do during the actual O&P exam. The school will guide you.
That's my experience when I went to Avtech. In the 5 days of O&P preparation, all that AVtech taught was in the O&P exam.
And yes, the O&P can take 2 days. I did mine in 1 day (started about 9am, finished just before 5pm with lots of break in between plus 1 hour lunch break, which the examiner took me out for a treat. I did very well & fast in the oral part. The examiner says it normally takes 3 hours to finish the oral part, I finished it in just under an hour.
The practical part of course takes time... plus my riveting and use of a multimeter sucks...