Frame restoration is not a given if your truck is to be a dependable work truck as you mention. The frame components such as steering and brakes would certainly benefit from a refurb but unless the frame has rot it may be good to go for your needs. A little surface rust is typical. I might suggest getting after it with a knotted wire wheel on an angle grinder and then coating it with Zero Rust and their "Crystal Coat". It will dress up the frame and give protection from additional corrosion. These products are available in rattle cans and are very easy to use.
If you can restore your truck on the frame then I would do that. These trucks are very easy to pull apart but the re-assembly is where most project fail.
If you could provide some pictures of the truck then others can provide their opinions if a frame off is necessary. Many times it is not.
