I like the interior. Checked NADA for Arnold,MO zip code 63010, and without knowing the specific additional options, the low retail is $5,600 and the average retail is $6,750. $8,000 IMO is a little high, espically if you need to replace the tires.
Can't add anything else to the good advice so far - espically the tires.
This includes double door refrigerator, air conditioner, stabilizing jacks, spare tire with carrier, and exterior shower.
Checke the following links - not made clickable intntionally:
http://www.nadaguides.com/RVs/2004/Used/Timberland
http://www.nadaguides.com/RVs/2004/Timberland/M-28-Windjammer/4079640
http://www.nadaguides.com/RVs/2004/Timberland/M-28-Windjammer/4079640/Values
The second link is where you would include options in addition to those listed above - for instance ducted AC. Can't tell if it has this, but if so, the value increases
Be sure to get the Gross weights and ensure your tow vechile can handle it - research payload - not just towing capacity. NADA lists the weight at 6,600 lbs. Not sure if theis is Gross or dry weight.