Help please.

1) your physical size (both height and weight are important)
5'11'' 157lbs, 15 y\o. 16 in december

2) How physical / aggressive are you ?
im pretty aggressive about 7 1/2 out of 10

3) what do you plan to ride- MX/SX tracks, woods, fields with friends or ?????
fields, woods

4) Do you have any riding experience?
no, i've rode some auto clutch quads though

5) Do you think you will race ?
nah

6) Are you mechanically inclined and will you be doing your own bike work?
i could probably do small things. not so sure if i can do something like a top end.

7) Do YOU have a preferance to a brand/ motor choice (2 or 4 stroke)?
i want a 2 stroke. not a kdx because they are too expensive in my area

8) Do you have a dealer close by your home that you might use and what brand(s) does he carry?
craigslist is my best bet.

9) How much ($) do you plan to spend on a bike?
< $600

10) Do you live in California?
nope, rhode island

11) Your age?
15

12) anything else that you think would help form an opinion
i found an 88' cr 125 on craigslist. it looks good, but he is asking best offer, and i'm not sure what to offer.
here is the post.

http://providence.craigslist.org/mcy/893674775.html
he put a video of it too
http://www.youtube.com/watch?v=1s1PqasiqxU

does that look good? and if it does look good what should i offer?

Do you think offering 400 is too low? My budget is really around 700 but I need 100 for a good helmet.

edit: he said he might be selling it today. i asked him when the last time the top end was rebuilt and he said "as far as i know..never" so i'm not sure if i want that very much.

I found another bike.

The guy selling it says it's a 91-93, but isn't sure.
He's selling it for $300.
He says it needs rear brake lever bolt and kick start rachet (are those parts expensive and hard to install?)
here's the listing:
http://providence.craigslist.org/mcy/894520088.html