batteries?

Much could be written to answer your questions but, I'll try to be brief. The battery(s) you choose will depend on the type of camping you do and how much power you usually consume.

If you camp a lot without hook ups, two 6 volt golf cart batteries will yield the most available power (amp/hours)between charging. These will not be inexpensive.

At the other end of the spectrum, if most of your camping has electrical hook ups, then a single deep cycle/marine ("hybrid") would be fine. Battery power is just required while you are in route to/from your destinations. Understand however, with this arrangement, you will not have much power for those times when you do not have hook ups.

Personally, I run two of the deep cycle/marine type batteries and use a generator when "dry" camping for several days. This arrangement gives me about 50-55 usable amp/hours between charging. I do not like to let the batteries get below 70% "state of charge" (and neither should you).

Here is how the math works: 2 batteries at 150 amps (each)"reserve capacity".
To convert to amp/hours, multiply by .6.     300 X .6 = 180 amp hours. This sounds like a lot of power but, remember, we can only use about 30% of that capacity before the batteries are dead. If we discharge much more than that, we can damage the batteries. So, 180 X 30% = 54 amp/hours available for me to use between charging.

These 54 amp/hours can last for days, with light usage. With heavier usage, I am recharging daily (sometimes, more than daily). Two 6 volt batteries (@225amp/hours, wired in series to yield 12 volts) would yield about 67 amp/hours (@ 70% state of charge) but, under heavy usage, I would still likely be charging daily. It did not make much sense to me to spend the extra money on golf cart batteries, as I would still need to carry a generator, anyway. The golf cart batteries will tolerate a more severe discharge but, at the end of the day, if I use 50 amp/hours, I'll need to put those amp/hours back in the batteries. Do I want to charge for a shorter period daily or, a longer period, perhaps, every other day?

Where you buy batteries is probably less important than making sure the batteries are "fresh" - less than one month old, preferably. There will be a "date code" sticker on them, somewhere. Dollar wise - I spent about $160 total for my two batteries, a few months ago. 6 volt batteries were in the $200 each neighborhood. The golf cart batteries will last longer but, I can replace mine and still be money ahead.

Personally, solar panels would not work for me. I like campsites that are shaded/wooded. I carry a generator.

Give some thought to your individual situation and "camping style" vs. how much you are willing to spend. What is best for me (or another) may, or may not, be the best answer for you. If we think of batteries as a "gas tank"- a bigger tank will allow us to go further between refilling. However, we will use the same amount of fuel to get from point "A" to point "B". How much you use and how often you want to "refill" should guide you in the direction you want to go.

I'll leave it to others to address the slide problem. Most slides that I am aware of have a manual crank - just for emergencies.

Unless you full-time, it makes sense to put in the cheapest deep cycle you can get, IMO. Every time I price things Wal-Mart comes out the cheapest $ per amp. If you are getting a generator I would stick with a single battery, too.

Make sure your lights are LED, and convert them if they aren't (an easy job). They are the second largest energy user after the furnace's blower.

Personally, I usually go to Costco for batteries and buy the Kirkland deep cycles.

I plan to replace my lights with LED's.  I would appreciate to know what kind, product numbers, sizes etc. of LED's so I don't have to experiment.  Anyone out there with that information at the tip of their fingers.  Also, does Forest River sell frosted light covers?  To my mind, the light from an LED can be pretty harsh.  Does anyone have a solution for moderating the light of LEDs?

Here is a link to the Lippert Components sofa slide out system. Look at page 10 figure 8 and it shows how to retract the slideout It's the slide mechanism that's on my 2012 177

https://www.rexandsonsrvs.com/manuals/lippert%20Sofa%20Slide%20Manual-Web.pdf