Newbie with ABS Module - doofy questions

I'm a newbie who just purchased a 2005 Prius with intermittent ABS problems: red BRAKE light and (!) lights come on with a high-pitched alarm. I just found paperwork from a year ago, when a previous owner took it in for diagnosis of the same symptoms, with error codes C1256 (Accumulator Low Pressure) and C1391 (Abnormal Leak of Acc Pressure). She was quoted $3,800 to replace the ABS actuator assembly, which I'm assuming she didn't do.

After reading myriad ABS-oriented posts on this fabulous forum, I figured I'd attempt to replace the ABS module myself, but have some questions while I await my parts. Many of these questions are downright silly, but I figured it would be sillier NOT to ask, so here goes.

1) The service manual frequently references an Intelligent Tester. Is that the same thing as a Mini-VCI and Techstream?

2) While I'm awaiting my Mini-VCI plug, I pulled the blink codes and got the following:
(!) -- codes 52, 57
ABS -- 42
I think I figured that those are shorthand for error codes c1256/57 and c1252. However, I'm confused about ABS 42 -- it might mean "you have another error in your brake system" or maybe "Open circuit in IG2 circuit ABS No.1 relay ABS No.2 relay Harness and connector." Can anyone offer some guidance?

3) The manual also suggests checking the resistance on various circuits on the accumulator. Silly Question Alert: do I need to do this actually at the accumulator, or is there another, more accessible end of the cable that would yield the same results?

4) The ABS pump seems to run a lot. Since the previous owner paid $250 to get the diagnosis that a new accumulator was needed, I went ahead and ordered a used one. Now I'm wondering if that was premature. Is there anything else I should test while I'm awaiting the new module and Mini-VCI plug?

Thanks in advance for your help.