I'm not sure where you are, but here in NC we have very hard clay and my neighbor had a system installed using the "pipe puller" which is trench less. I sat and watched the machine work and the first thing I noticed it was not burring the pipe deep enough and he will have problems aerating the lawn. This fall he aerated and seeded. When he turned on water it was leaking from everywhere. Also, even if you hit the pipe and did not brake it right away it will put micro cracks in the PVC and over time it will crack.
Contractors love to use it because it saves them time and money. Pay the extra bucks to have it trenched and don't worry about the extra mess you will never have to worry about hitting pipes.
Or install it yourself, If you think you might want to I can shoot you a web site that is the best on the net for do it yourselfers. Do not use the free design offers from the manufactures or you will be sorry!
I also have some other tips for you if you choose to have a contractor install your system, that will have you some major bucks down the road.