My crappy lawn

I have been quite unsuccessful trying to get my lawn to look decent since I
bought the house nearly
4 years ago. I dont have money for a landscaper. Below are links to
pictures that I took. 

The first pic shows these clover-like things growing in patches.
http://i231.photobucket.com/albums/ee225/trusso11783/lawn1.jpg

This next one shows leafy type growth for a big part of the lawn
http://i231.photobucket.com/albums/ee225/trusso11783/lawn2.jpg

This is a picture of the entire lawn. It is very wavy and unlevel.
http://i231.photobucket.com/albums/ee225/trusso11783/lawn3.jpg



For a short term fix. is there a way to get rid of those growths described
above so that they are
gone forever and replace with grass?

Is it just better to rip it all up and start new? As I said, i cannot
afford landscaping services
right now but if I have to hire one guy to rip it up and level it, what
would that cost on Long
Island, NY?  Once it is leveled, I could probably seed it myself or get a
friend to help me.

I am looking for constructive answers please. Do not reply that if I want
something done, I have to
pay a pro to do it. That isnt true. I installed hi hats, re-wired my house
with new power and light
switches, remodeled most of my bathroom and did plenty of other things
without paying a pro. I am
pretty good at doing things.  I just dont have a green thumb. Thanks.

Tony