Ok, for the wsp part follow laurie, or if your lazy add wspbuilder to visual studios to build the wsp for you.
now to add the masterpage and css:

create an empty project

add module

as you can see above, remove the sample.txt, right click styles and add your masterpage and add another module for css :)
for the css, click on the elements.xml and add the following:
Url = “Styles Library” and file Type = GhostableInLibrary
<Module Name="Styles" Url="style Library">
<File Path="Styles\newstyle.css" Url="newstyle.css" Type="GhostableInLibrary"/>
</Module>
the first part Styles\newstyle.css is the module name and then the file name, the url is the location you want it in. The module url is the location you want to add this to.
for masterpage:
<Module Name="Module" List="116" Url="_catalogs/masterpage">
<File Path="Module\Sample.master" Url="Module/Sample.master" Type="GhostableInLibrary" IgnoreIfAlreadyExists="false" />
</Module>
same as the css the masterpage is the same, Module\Sample.master module is the module name and the sample.master is the file name within the module within your project. the module url is saying to put the file within the catalogs area.
for images and for page layout files can be done exactly the same way!
reference:
masterpage: http://www.c-sharpcorner.com/uploadfile/anavijai/creating-a-custom-master-page-in-sharepoint-2010-using-visual-studio-2010/
CSS: http://blogs.msdn.com/b/vssharepointtoolsblog/archive/2009/11/23/how-to-deploy-a-style-sheet-into-content-library-using-visual-studio-2010-beta-2.aspx
page layouts: http://blog.beckybertram.com/Lists/Posts/Post.aspx?ID=71
http://blogs.msdn.com/b/kaevans/archive/2011/04/02/code-behind-page-layouts-with-visual-studio-2010.aspx
image:
add image to the module folder, your elements file will look like this:
<Module Name="Previews Images" Url="_catalogs/masterpage/$Resources:core,Culture;/Preview Images">
<File Path="Preview Images\image.png" Url="image.png" Type="GhostableInLibrary">
<Property Name="Title" Value="Custom Preview Image" />
</File>
</Module>
or instead of module just create the directory within your project 14/template/images add the image files within this folder will add them to 14hive image folder.
http://msdn.microsoft.com/en-us/library/ee231567.aspx
as i said above you can do laurie's way or.... use ms build:
On the Windows Start menu, choose All Programs, Accessories, Command Prompt.
Change to the directory where your SharePoint project is located.
Enter the following command to create a package for the project. Replace ProjectFileName with the name of the project.
msbuild /t:Package ProjectFileName
example, you could run one of the following commands to package a
SharePoint project called ListDefinition1.
msbuild /t:Package ListDefinition1.vbproj
msbuild /t:Package ListDefinition1.csproj
http://msdn.microsoft.com/en-gb/library/ee231588.aspx
or you can use wspBuilder (which i use), download it, install it to Visual studios and right click your project.. select wsp build, select build wsp. The wsp will be added to the project for you. If you goto the directory where you can see the project files youll see the wsp there aswell.

http://wspbuilder.codeplex.com/downloads/get/94507?releaseId=30858&ProjectName=wspbuilder
before build:

build (ignore the cmd as your using vs2010 build not cmd)

after build

I hope this answers all your questions! Iv tried to make it as simple as possible! your tasks should be very simple... once you have done one module the rest is very simple todo and easy to understand :) , wspbuilder is easy to use and fast for creating as you dont need to do any manifest as it does it for you!