On a side note: like others have said, the core theme is very old and you almost certainly will have issues with it down the road if you try installing more mods due to them not installing cleanly. I would recommend using the default SMF curve theme or try looking at some of the newer themes that have been released.
Also, I think most people with no coding experience are probably pretty nervous about manually editing in code on their forum at first. Personally, I think that's natural.
What I would recommend is creating a test site as well, so you can practice making edits in templates, moving lines of code, etc. If you make a mistake, it's just a test site so no bid deal.
You should also be creating a backup before installing or uninstalling a mod. You should aslo backup before editing a template or source file. For example; if a mod is letting you know that say index.template.php file will fail during install, you could back up that file and then manually edit in the code that mod requires into the template. If you edit in the wrong place and your forum becomes unusable, you can just upload the original template you backed up and upload it back as if nothing ever happened and try again. (this would all be after you did a complete back up of the entire forum of course
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