Questions about upgrading 1.5.1 to 1.5.3

Hello and thanks in advance for any advice that you can give on doing an upgrade from 1.5.1 to 1.5.3. :D

First off, this is my first time doing a Zen Cart upgrade. I have been using 1.5.1 for about 4 or 5 months now.
I have thoroughly read through the upgrade instructions that come in the Docs folder of 1.5.3. I have already used Beyond Compare 4 to note any and all changes that have been made from the original untouched version of 1.5.1. I came up with about 20 pages of changes in the files between the mods and the code changes I have made to zen cart. A good majority of these noted changes I found were from mods that were installed. I also went ahead and compared the template I am using with a clean version of the template and found about 8 pages of mostly minor changes to the appearance of the template.

I am running in to a bit of confusion on the next step to take complete the upgrade.

First question: When in the process do you re-install the modules that you were previously using.

Second question: When do you install the module that you were using in the previous version of Zen Cart?

Third question: Are you essentially just scrapping the original version of Zen Cart (in my case, 1.5.1) and rebuilding everything on the 1.5.3 and upgrading the original 1.5.1 database from the original live site and using the zc_install to upgrade the database to the 1.5.3 version?

I apologize in advance if I am making this more complicated that it has to be, but I just want to make sure I do this correctly and minimize my change of screwing something up. I really just want to understand the process better.

If anyone has any suggestions I would love to hear them. :yes:

Thanks again,
Chris

For question #2, I meant to ask when do you install the template you were using in your live site before the upgrade.

Here I m trying to write out some guidelines and what I can tell is that I am not able to write out every example of how this could be done, there is no right way, it is in a wy sometimes an art, sommetimes a science. Obviously if one does a lot of database related work/install then restores the old database, duh lose all of the database work, but when performing an action and now something doesn't work, the evaluation of why... Is it because need to back step or is there something in the next step that needs to be done??? So, I expect the below to be torn to shreds, but offer it anyways. Seems to me I would have to write a book to address how I might approach the entire process... Perhaps breaking it down more would help...

2. If you know you are adding plugins, adding the template before adding plugins would be the preferred route. It may be a time saver to update the database before installing the template. Work out any issues with displaying content, then continue to modify the content by adding/verifying functionality of plugins.

3. The files that will be running on the server will have the content of the 1.5.3 version plus plugins. How one specifically gets there whether deletion of everything and then copying everything over or overwrite everything and delete the extras off after/while copying over, there are a number of ways to get there. Ideally as quickly as possible without allowing outsiders to poke at the momentary transition. But one thing is that whether the database is upgraded in place (zc_install) or it is upgraded remotely and then copied over (not suggested unless the site traffic has been stopped and there is a potential password issue if different php versions are used) the zc_install process of updating the database is still performed on the data that will end up on the live site.

4. If you are completely rebuilding your site, then this would be second or third depending on how the above has gone and the overall process of installation/upgrade of each plugin. Ideally, the version of the plugin being installed is the sme as the version previously used and is compatible with the new zc version. If not, then have to understand the impact and adjust accordingly, but the majority of plugins will behave appropriately for this level of upgrade if they support 1.5.3.