OOps! @Goodywood, don't get bogged down and overwhelmed. There is a lot of store content. Break it down into chunks.
1. You rename your old sims folder so a new one is created.
2. You patch that up to the latest store patch, which you can do by simply copying your old contentPatch folder over (or just the contentPatch.package file from the old folder to the new one).
3. You download and install all the store items that have unique patterns with them. (There are only a dozen or so of them.)
4. You can also download and install the items that were left out of sets accidentally (like a pair of high heels) or that, like the dining room chair, was fixed later; but not in the set.
5. Then install your biggest store world.
6. At this point, your first .ebc file in your dcCache folder should be about full.
7. This is where you MOVE that file to a safe spot (like a folder on your desktop that you call EBC) and then install more, so you only have one .ebc file into which you are installing at a time.
When, your .ebc file is getting full, you rename it by only changing the 0 at the end to the next number in sequence. So the first file remains unchanged, but each new one will have the 0 changed to 1 the 1st time and 2 the 2nd time, all the way up to 20 something, depending on how much store stuff you have and want to install.
I did this in logically batches, starting with worlds. I looked at the SIZE of each file and grouped them to get the max amount in, without going over.
So, my spreadsheet shows what I put in each of my .ebc files on the first tab. Each of the other tabs is grouped by type and shows how big the file size is and how I grouped them together.
You can make your own determination of how to group your files by looking at the approximate file sizes. Every system will be a bit different and even the order in which you install them will change the file size a bit. (Sometimes I had to reinstall the items in a file in a certain order in order to get them all in; so, the spreadsheet also shows the order in which I installed items.)
When you finish installing all your store stuff, change that last file number and move it the folder where you put the others. If you keep this folder in a safe place, you can then simply copy and paste it whenever you have to, or want to, start a vanilla sims 3 folder.
Does that help at all?