I have done Pennsy models before, as well as Alco imports. This one already has a can motor so no re-motor (a huge plus), and a headlight so no drilling of the headlight casting. If she wants the backup light for the tender that one would have to be drilled. The tender chassis is drilled for a speaker, so that's a plus. The modifications necessary would be:
A hole cut or drilled in the rear of the loco chassis, probably under that folding deck plate that spans between the loco and tender, and a hole in the tender front. These holes are for the wiring harnesses, there would be two if I did it, a three connector for the loco chassis and the two motor leads, and a two connector for the headlight. The harnesses could have plugs so the loco & tender could be separated or you could hard wire them and have the tender permanently attached which would rule out using the original box. I generally use harnesses by Miniatronics unless the customer requests hard wiring. I'd say five out of ten for complexity. Probably a new light bulb and new lenses too.
If she has a local shop that is capable, the modifications are pretty basic. The questions are, is there a local shop and is it capable?
One caveat: I am not familiar with this particular model and would have to have it in hand to be sure of the above. Most installers charge by the hour and usually qualify their estimates with a plus or minus 20% statement. Brass models can be full of surprises!