All I can say is dont mess around and dont go cheap because it could bite you big time. If you're lot is big enough, Id probably go ahead and lay a new field since it sounds like the existing one has stopped perking. Keep in mind, its hard to sell a house later on with an inoperable septic system. Do it right and get it over with. Get multiple quote/professional opinions.
Yah, one issue that i am worried abotu is the lot really isnt that big, maybe .7 of an acre
Out of curiosity, how old is your house/septic system?
house was built in the 50's no clue about the tank, guy said looked to be 20-30 years old