Trolling Motor advice needed ASAP

This time next weekend, I'll be installing my new trolling motor on my
Nitro. Currently, it has the Motorguide 43lb 12v, and I'm going to finally
get a 24v. I haven't yet decided on which one will be the replacement, but
I'm looking very hard at the Minn Kota Maxxum 70lb, 24v. This one is about
$700.00 at BPS, and the one with the universal sonar is $80.00 more. (figure
in 9.75% for taxes and about $20.00 shipping)

Would you feel the universal sonar is worth the $80.00 difference?

What am I going to need to convert the 12v system to 24v? I already have the
battery installed, so how are the two connected at that end, as well as the
plug end? I'm thinking that all I need to do is install a small connector
between the positive terminal to battery A, to the negative terminal to
battery B, then connect the trolling wires to the other terminals. At the
female plug, I should just has a single 24v, and that's where I should
connect the wires inside the male connector. Sound right, or am I missing
something?

Now for the battery charger... I have a Pro Mariner two bank charger. How do
I connect it to a 24v system? As of now, I have one bank feeding one
trolling battery, and the other feeding the starting battery. I'll move the
ones feeding the starting battery over to my spare trolling battery whenever
it needs I think I need to charge it, but it's usually connected to the
starting battery. Would I need to purchase a three bank charger now, or buy
a single bank charger for the starting battery? I get really confused at
this point... LOL

I don't have a clue as what the breaker size is on the 12v motor... what
rating should I look for if I think I can use it on the 24v system?

The only other problem that I can think of now is the power connections to
my bow depth finder. I've got it hooked to the trolling system, so I guess
I'll have to re-route the wires to the 12v system under the console. Not a
big problem, but maybe you've got a secret that I haven't thought of yet.

Thanks for any help/advice.

Charles