First of all, you say "seemingly great reviews" What is that supposed to mean? does she have great reviews or not? do you have VIP here? If not, then you should get it. the only way to read the important parts of the riviews is with VIP membership. This will also allow you the use of the PM system where you can PM other reviewers to get more infomation. The VIP membership is only 30 bucks a month and it will more than pay for itself with one visit to a provider. (due to being able to do the correct research and not getting ripped off etc.)
Read the self help manual (located at the top of the page under the life preserver) There is lots of good information there. Also read back some pages on this board, and use the search feature on the top of the page, and search for "screening" and 'verification." You will see these topics covered multiple times
As to your specific questions,
1) The advantage of using a screening service is that you will give out your screening information one time (to the screening service), rather than giving it out multiple times to many different ladies. There is probably less of a chance of the info getting into the wrong hands with the the second method. Most ladies are very good with your information but there are some careless or unscrupulous providers out there so you never know. Also if you use P411, they are based in Canada, so it is very unlikely that your info can get into the hands of the USA LE. Another thing about P411 is they will work with you. They have ways of verifying unemployed, self employed, retirees, military personell, college students, etc.
2) Definitely get a prepaid "burn" phone. It is called a "hobby phone" in this hobby. Do a search for hobby phone also on this board. You will see numerous threads. When you are searching for topics, change the day range to a longer time. (the default is set to 30)