does anyone recommend a service or a course for learing to do short sales? i would like to target this strategy but need to learn more about it.
You should start by listening to all the great free audios on this very site. Read as much as you can article-wise from this great site as well. Do as much as you can for free… and then you’ll see where to go to get the best info.
Some of the “gurus” teaching short sales right now are Dwan Bent Twnford and Bill Twnford, Mark Sumpter, and Mark Ijlal here in Michigan. There are many MANY MANY more, those are jsut the three that popped in my little brain at this moment. 
READ AND LISTEN TO EVERYTHING ON THIS SITE!
As someone who is in the very beginning of my first short sale I’ll share with you how I got from zero knowledge whatsoever to be reasonably equipped to work a short sale. I began by reading this forum. The information is priceless. In fact, you could probably make a book containing many of the posts and sell it at Barnes and Noble for $29.95.
About three months ago I hooked up with an investor in my area doing short sales. I brought him deals and was paid 10% of the net profit. After several deals, I pressed and became more involved. Tell them that you want to become a successful investor. By bringing them deals, they will make money and be open to giving you a fairly in-depth look at the business. Ask to sit in on meetings with homeowners, take part in conference calls with loss mitigation etc. During this time, I made some money and got a great education of sorts from my mentor. Consider the deals you bring them as tuition for the knowledge they give you.