Question
I have lived in my existing home for only a year, and this is the first lawn I have had to care for.  Last year we used a company called weedman to rid us of all the dandelions and fertilizations.  What I seem to have now is a full spread of broad leaf, as well as some sort of weed that looks like grass but has a seedy head.  I have also discovered some spreading of Mushrooms.  The soil from which I pulled them had a spongy white substance, some sort of thatch I presume.  What should I do?  Luckily I have Sold the house and will only be here for a couple more months, but would like to learn, so I can avoid it in my newly built house.  

Thanks,
Chad

Answer
Chad:
A multipart question, answered as follows:
I do not know where you are located.  However, the broadleaf weeds may be treated with a 2-4D variant, a combination of 2-4D and other herbicide.  Follow your local ag extension agent's recommendations.  He/she may identify the grass of which you wrote.
I would not worry about the mushrooms.  They will be gone after the full moon and when hot weather begins in earnest.  The white mass is the mushroom "root sytem" or underground propogation system.  It will disappear when the fungus is not in fruiting stage.  If these are the edible field mushroom, agaricus campestre, properly identified, they are valuable.  People pay good money for them and you must be in the middle to upper east coast to have them volunteer so readily.
To avoid these problems in your new home, make sure the soil is properly prepared and clean of wood mass underground (roots, trunks, limbs.)  Seeding should be done at the correct time for the species of turf sown with the best cultural practices available.  Seed variety is critical.  Choose one recommended for your area.
One recommendation for soil prep:   Use a high quality compost for soil prep or to topdress seed if a winter grass is sown.  Less than one yard per thousand square feet is a high application.  I have used 1/3 to 2/3 cubic yards per thousand feet with good results.  A high quality compost for this purpose should have high N, or approx 2-3% N.  If it is still good compost but not high in N, fertilize with some supplemental N after topdressing.
After sowing, follow recommendations for watering and weed control.  Establishment of a good, thick turf
is a two to three year project.