best method for finishing.......

I carry waikong's idea one more step.  Apply a coat of flat after decal have been applied, weather with pastels and then add a final overall coat of flat.  Pastels hold to a flat covered surface better (more "tooth") and the final coat protects the pastels from handeling etc (about once a year I dust my models using an old shaving brush - after the second time, the pastels are gone from the model)

I would gloss with future over the whole thing, and then flatten everything after decaling. If you use pastels or weathering powder, use it after the flat coat.

If oyu are used ot spraying enamales and feel more comfortable, an altermative to future is Model Master gloss lacquer.  Goes down t like any other enamel.  theonlything is you will have to used an acrylic or pastel wash, the latter being my new favorite. An oil wash will take off the gloss with the wash

Here is my finishing procedure:

Paint
Clear
Decal
Clear
Wash
Flat
Pastel
Flat
Pastel

I use Future, and I clear the entire model with an airbrush...it takes some practice. Check out the Future Sticky and check out Swanny's Future site:
http://www.swannysmodels.com/TheCompleteFuture.html

I understand your anxiety. I would practice on a test model before applying the clear. I have an old B-25 kit I built as a kid, that got really damaged in a move and I use it to test new techniques. It has a very interesting paint scheme on one wing right now. It will probably get a dunk in Castrol Super Clean soon...

You can also use a plastic milk jug to practice in a pinch, but I highly suggest the "test" model. I would get a cheap one on flea bay or from the bargain bin at your LHS...slap it together and there you have it. It really helps getting over the anxiety of trying out "new" techniques.