I will first tell you that you should not be basing your decisions solely upon what you are being told on this site, we are not accountants or attorneys. I highly suggest you make an appointment with your accountant or financial attorney to discuss what will work best for you and your business.
When I formed my LLC, I met with my attorney to discuss my options. From what I found, a Sole Proprietorship is easy and cheap to set up but offers you very little protection. Under and Sole Proprietorship, your business and personal finances are basically seen as "one", so if you were to have a lawsuit filed against you, they could go after everything you have from your truck, trailer, equipment to your house, personal car and other personal belongings. However with an LLC, it will separate your business and personal finances. Again, should you be sued, they could only go after your business, not you personally, so your house and other personal belongings would be safe.
Be careful when you write a newer truck off on your taxes. A lot of people basically spend a dollar just to save a dime. There's more to it....
Again though, make sure to make an appointment with an accountant or tax attorney to discuss your options. Spending a couple hundred dollars now, can make life way easier for you down the road.
'07 Chevy 2500HD
2010 John Deere Z925A 54" MOD
2011 John Deere Quik Trak 647A
John Deere walkbehind