Also, I used to have metasequioa and Doga on my computer, so I cannot remember 100% of everything, but I try to give you my best advice.
First you will probably need to find a key for metasequoia, in order to import/export other file formats.
Here is a guide about saving in metasequoia, make sure you have read it before moving on:
Second, you can export to Doga two ways:
A. Go to "File", and I think either "Export to Doga", or "Save as part file". If you have Doga installed already, then a little Doga window will pop up asking you how you want to save. Typically uou create a new folder or "part group", and then click and empty space. Then tell the program you want to save a new part by either click a button that says "Save", "Add", or "Render". This method allows you to bring a part that you can color using Doga.
B. You go to "File" and "Save as/Save". Then you click and make sure you are in the right folder you want to save your new part in. Make sure it’s a folder you can easily find. Then you make sure that you have .suf selected and follow these instructions here at
http://trlibrary.tripod.com/id55.htm. Make sure you click "on" the button that talks about "keeping colors", "keeping attribute file", or says anything about ".atr". Then you hit save and open up Doga. You import it just like you would a normal part in Doga. However, you make sure to import the .atr file as well so you can edit the colors. You edit the colors of your new .suf, by opening the "palette or .atr" file with the same name as the .suf, changing around the colors, then re-saving the new palette under new name. Then you either minimize Doga or hit render and the part will change to the new colors.
Note you can store more colors than the part actually uses in the palette; however, the part will only use the original "names of color mapping" it had when it was made a .suf . If one of those colors is missing, it will default to white/grey or black.
Here are some other tutorials on Meta:
http://www.youtube.com/results?search_query=metasequoia+tutorial&aq=f
http://www.angelfire.com/la/bryde/tutos.html
http://trlibrary.tripod.com/id49.htm