Tom,
I had magnetics made up for my pick-up before I got the vinyl. When I tried to put them on the other truck the paint on my ex-asplundh doors was too thick for good magnetic holding power and the sign came off in the wind. I don't think that the box has as thick of paint. The indents would not allow the sign to magnetically attach, but maybe in the spaces in between the indents.
I found out that the vinyl letters have a sticky backing/ transfer paper of some sort that hold the letters together. With my old white paint (repaint), I got a lot of little blisters in the paint that popped the paint off. I imagine that a fresh repaint will not have that issue after its fully cured, just maybe a thickness issue for magnetic, but maybe not.
Magnetics are a potential liability. If one peels while going 70, or in the case of my truck 58mph, on the highway, it could cause an accident, which could come back to you.
Paint will go a long way to represent you well.
Bolt-on signs could cover the asplundh name until you get it repainted.
Vinyl can be done in stages to spread out the cost.
I was quoted about $500 per side for 4'x8' signs on some plastic laminate sign material at a local independent sign shop that a customer owns.
I ended up paying about $1000 for the lettering on my pick-up, chip truck, and chipper.
You'll figure out what's best for you.
Something else though is that if anything is broken, preventing you from working, it won't matter how good your truck looks back at home.
It might be good to focus first on getting an inspection, check your transmission and differential oil levels, etc.
See if you need a DOT inspection, if you are likely to have to go past any weigh stations especially.
ENJOY!!!!