OK, found Header and Footer plugin - thanks for the tip!
Will be checking how to use it. Hopefully it will allow me to do things I can't because lack of orientation in css or php topic. Could you explain to me or point forward to a good source on that matter?
If I'd ignore the plugin you mentioned, I have few basic questions that I must know first but don't know how to find them quickly.
1) if I write/copy a custom css, do I create a new file from the scratch or edit a proper one (in second case which one and in which place?)
2) where should be this new file be placed? in WP, woocommerce, plugin, theme directory? in which folder specifically?
3) if I create a custom css, do I need to change some things in php to link it to a new file or css line or is it enough to put a file in right place?
4) how do I recognize in which place of a code should I add my code if I add something new?
I am aware that you can't guide me step by step, because it would take too much of your time. But if you know some site where I can quickly find that stuff without extensive reading, I would appreciate.
I'm not so retarded in this area not to be able to make some custom cod fixes on my own (even in php) just by playing with it and experimenting. However such a route takes LOOOOOOT of time and I don't have such luxury lately.
And thanks for response. I hope I will be able to dig deep enough to follow with the changes you suggested.