Of course your degree in Construction Management and Technology would be very helpful for a practice focused in that area. You may even qualify as an expert in the area and pull in some big bucks as a witness. But I have seen it happen that people entering law school with the idea they will focus on a particular career get sidetracked or discover other areas of the law they like more. Just do it and see where it takes you.
no, you don't need a lawyer. once your school has accepted you, issued you an I-20 and registered you in the SEVIS database, assuming you remain in status on your B1/B2, you can file an I-539 with USCIS to change status from B1/B2 to F1. chances are it will be approved, but it's not guaranteed. if not, you'll have to leave to get a student visa to return. you won't be able to start class until it is approved though, and that might be your bigger problem. it will probably be faster once you have the form and are registered to apply for a student visa outside of the US. check out www.uscis.gov for more information and forms.