[font color=\'#000000\']I agree with Erik, but have a cheeper method of testing the waters. Rent a system a few times, or better yet, rent several systems. Also you can call some industry reps and get a free demo. Don't buy the first system you think you like. Try as many as you can get your hands on.
I can tell you this, your going to like the digital backs over the the SLR type. The resolution is worlds better and more conducive to professional applications. If your biggest concern is portability, than you still have plenty of options. But your talking about an outlay of at least $10,000-$25,000. So again I say rent. I have known photographers who have rented systems by the job, and have done this for years. After you have done this for a while, and get comfortable with a system, than take the plunge.
One last thing. keep your film equipment if you can, I still shoot some film and I've been Digital for 5 years.