Hi Tech
You can try different compressed formats when the paint is done, but paint it in 32 and then you have the best quality and retain all the options.
I have not used DDS yet so I can't coment..but again start high and go down to it.
If they are supplied compressed you can't decompress and get the quality back.
It may be an idea to check arround for a paint kit.
Sometimes the seller has one and if not then sometimes others painters have knocked one up and pass that on.
Failing that.......
Your best bet would be to use chunks of the existing if necessary and use the rest as a templete and draw new lines etc over that, again using seperate layers.
Some details you may have to use ..like photo textures for wheels or wheel legs..perhaps engine/exhaust detail.
If that is the case then chances are they won't show on those small areas
It is the main airframe surfaces that are important and even though it is a pain and time comsuming it is worth overhauling the lot.
When you have finished I am sure will see the difference and see how worthwhile it was to do that.
There are no easy answers in repainting and no magic one fix for all formulas.
Just take it step by step and do each on it's merits.
Two things when starting out that are worth remembering
You can't use too many layers. It is useful to keep them seperate and can be combined later in a copy . I have about 50 layers on the HS 748 paint kit I made and about the same on the Argosy. My Superfreighter has more than that now even though it's not finshed as idividual parts are added and textured. Always make sure you have a master layered document as a back up
The other thing to bear in mind is you can't fail
Even if you get fed up with a job and throw it you will always have learned somthing on that job. Things rub off as you work on the paints and daunting it may seem at first some of it sticks and the knowledge grows
If you get stuck then post here and someone will soon answer.
Individuals have different ways of working so spread it arround and soon you will find one that suits you.
Don't be afraid to ask anything you may feel is trivial as we were all newbies once and most question we have answers too because we once asked them ourselves. ;-)
I'm sure you'll get there
ATB
Garry