The best thing to do is ring up your insurance company and get quotes for modifications.
That way you won't be shocked and have to undo your hard work when you phone them to declare it.
My advice is don't modify your car before you pass your test, because it may be cheaper to insure now, but as soon as you pass it will rocket it.
Just keep it clean and tidy up the bits that need doing.
Probably not what you wanted to hear but just my two cents!
Happy car cleaning, and welcome to the forum.