Preparing For HV Battery Replacement -Last Minute Tips?

Hello everyone,
We got a 2005 Prius that died and was traced to a bad HV battery. At the initial stage , the 12v was replaced yet nothing changed and then we had to source for a replacement HV battery. We finally got one- a reman from Dorman. Right now, the battery has arived and we are set to undertake a DIY replacement on in a day or two. [We've gone through some video guides on youtube (such as these:

,

(parts 1,2,&3) and gathered a few tips from this forum].

Present Condition of the Prius:
Right now, the newly installed 12v has been drained out -no light or power on the dash. The car has been down for about 5-6months while we tried to get a solution for the issues. For those of you who may not be aware, we are not in the US so it takes a while to get things done on it. So, for now, there is no power on the dash or in the cabin. Big mistake we made I guess was to let the new 12v battery stay connected all these while. Well, we just hope the battery would respond to charging...

Action Plan:
We plan to use the jump starting technique to power the 12v so we can open the boot and commence the HV replacement process.

Anticipated Challenges:
1. In view of the no-power state of the car, we suspect some configurations would be lost due to these power outage.
2.Upon completion of the battery replacement, what possible challenges are we to expect in view of the prolonged period of the car being left unused (about 5-6 months or so)
3. ???? (The Unknown challenges?? Unanticipated???)

Required Assistance:
1. We'll appreciate any guide that shall help us overcome the above listed potential challenges
2. We would appreciate any lesson-learnt from those who have gone this way before (replacing the battery) so we could leverage upon your experiences as we undertake this.
3. Any other suggested resources,inputs, links, ideas, last minute tips, check lists, etc in this regard shall be highly appreciated.

Thank you.

...Kay-Kay.

Hello everyone,