upgrading template

I am using this template but old version (for J1.7) and I wanted to upgrade to version for J2.5 (and later for J3) and I am not sure how to do it to keep my correstions in styles. It seems that I have to remove old template version and then install new one. But then I lose all the modification I made. Would it be enough to copy template_css (and .php) and layout.css from my older versions? Is there a differences in this template files from version to version?
Also how can I restore my template settings to the one I previos had (colors etc.) Is it enough to copy old params.ini file to new version?
Thanks

Update joomla change template files by copying. If you had some customization (Edits) in template files "Dzaba si krecio" you will need to apply them again. Be sure to create backup of files and db first.

Uf, complication.... Since there is changes from version to version
One more ... When I change setting via template setting and use custom setting (not predefined styles) they should be stored somewhere, could you tell me where does it store those settings ("farbe" i sl:-))
Thanks...

Another question...
I tried to remove Welness template (so that I can install newer version) but I keep getting message "cannot delete last style of tamplate" so template remains. I tried to install new version anyway but it doesn't goes through installation...
I tried manualy to delete welness template folder and then install new one but then I get a three listing of welness template in template menager (and all templates shows as ver 1.6)
Can you help me? How to remove template...? Specially if I have to remove it manually (what else should I remove)..

Table is #_template_styles , each record holds all template settings.
You need first to switch to other template (any other) before you could delete it.