Hello Dan, you don't necessarily need a toughbook. We have more than 8 laptops in this shop that have been used daily for years and none of them are toughbooks. They are just "middle of the road" laptops or cheaper.
They are not going dead from dust, so unless you are in an extreme dusty place, don't worry about it. Dropping a laptop would be very rare. Between 4 techs, a service writer, and the owner, no one is dropping laptops and killing them. That would be like a once in a decade accident, so not something to be over concerned with. Also, no problems with fluids getting into them. Why would someone use a laptop during a leak repair? Laptops are used for diagnosis and looking up info. There isn't fluids spraying everywhere all over the shop that you need to worry about.
The next question is about SSD vs. HDD. This is going to be personal preference for how much money you want to spend. The difference between them is the speed at which the laptop starts up, and the speed at which programs load. So, like when you are first starting picoscope up, that has to be fetched from the HDD(or SSD) on first start up and put into the RAM memory to run the program, but once it is up and running it doesn't matter, the speed is the same. Also, the difference in speed isn't significant. So, if you want to spend much more, then get the faster SSD, or save money and get the HDD which is just slightly slower.
I think you should be more concerned with the rating of the CPU, and the amount of RAM. More RAM is better, but again, it's all in how much you want to spend. Something with 8GB of RAM or more is good. When shopping laptops, look up the CPU rating here:
https://www.cpubenchmark.net/CPU_mega_page.htmlHope that helps