Question about the property appraiser for tax assessment?

I bought the house for 170,000 in 2007. The latest appraiser done by the government for my property tax was 156,000. But all the houses around us are selling for less. I went to the city hall and asked for a form to reevaluate my house value(I suppose the land value can not be lowered because all my neighbors share the same amount of land value). I'm filling up the form and am required to bring evidence. Here are my questions:

a. I need to list the sale price for 5 similar properties as my evidence. Can I use houses that are in other parts of the city but in the similar enviroment as ours?

b. Can I use the sale price of 1989 or any prices before the housing market got over-heated five years ago? Would those prices be strong evidences, useless evidences, or useful but not effective evidences?

c. Do I need to appear in court and argue with someone? or is it just a discussion in one of the city hall offices?

d. The house value was first evaluated by the government as $220,000. We asked to lowered it and they did. $156,000 was not bad, but many houses in the district are selling for less. Can we ask the city hall to lower our house value again? Will they change it back to $220,000 or maybe $200,000? My god, that would be a big problem.

When you submit your re-appraisal form and evidence, the City Hall people will review and make a decision (probably without your presence). You can use other properties in the same city as long as the areas are comparable. I have been told by the Assessor's office, that when someone challenges the assessment, they automatically adjust it down by at least 1% just to get you off their back.