Do my own pest control has some decent rat/mice poisons, but it depends on your state if they can ship to you. I've used both the Contrac (not available in CA) and Fastrac (Not Available in AK) for a roof rat infestation in a house that sits empty most of the time. Seems the critters eat more of the Contrac & leave the Fastrac for last. (as I understand it, there is a bittering agent added to the Fastrac to keep pets/kids from trying it as there is no antidote, so you are forewarned). I laid out both & started seeing/smelling dead rats within a few days.
As far as scanners, any code reader for heavy diesel should give you the codes. (Not Cheap and the connectors need to be matched) the Launch scanner x431 with diesel module is around 2k, the carnick scanner ls shows in the shop manual is over 3 k. The shop manual translates some of the dic codes into actual codes & provide daignostic procedures. Good luck on both problems.