Firstly, welcome to the server!
Making a shop in the market place; Do you mean buying the actual shop plot, or setting up the sign?
For buying the shop plot, you will need a total of 10,000.00 noobz. After that, it will cost you 200 noobz plot tax daily.
For setting up a shop sign; This is the set-up for that.
First line: Leave blank
Second line: This line is to put how many of a certain item you are wanting to sell.
Third line: This line is to show how much you are wanting to sell a certain item e.i B 500 : S 90 (I recommend using that to make a successful shop"
Fourth and final line: This line is to show what item you are selling, Some items have different names to what they are, so I like to use this website:
http://www.minecraftinfo.com/IDList.htm which shows the items ID number. If you do not want to go through this process, and if you have the item, put the item into your hand and type "/iteminfo" Which will show the item ID and the items name in chest shops.
For your house/base to become non-griefable, you will need to join a town to move it there. If you do not wish to do that, and you get griefed, type "/helpop I have been griefed" and a mod will be there to assist you.
You can spawn in your house by either typing "/sethome", but if you already have a set home, you can place a bed, sleep in it, and type "/home bed" which will then teleport you to your house! But don't break that bed, otherwise you will not be able to teleport there.