Few questions about water.

Alot of RODI's come with a few hook up options the under the counter tapping into the pipes, a hose spigot hookup or temporary faucet hookup that you can disconnect after making your water. Those that don't come with the adapters you can pick them up online or at home depot.

Slappy is right its not NEEDED but I'd highly recommend it unless you have awesome city water you'll likely face many algae battles. Initial fill up doesn't matter much if its tap or rodi though cycling with either your going to see some algae bloomage, probably a bit more with tap though.

Some sand you don't need to rinse, I've used a couple different caribsea's and just dumped it in the tank and added water no clouds.

My initial fill with my first SW was tap to start the cycle. Many people hook their RO/DI up to the tap then store in a closet when not in use. If using dry sand, yes you can rinse with tap water. If you are using live sand you shouldn't need to rinse it.

My initial fill for my 90 gal was just what you said, tap water dechlorinated using prime. I believe we have "average" water quality in my area. I didnt have a RO DI unit at the time and I was not prepared to lug 90 gals of water from anywhere to my house. Once I started adding live stock about 1 month in, I used only RO DI water though. My live stock(including a couple of corals) seems pretty happy at the moment-for the most part, my brain is finicky these days but I think its a completely unrelated problem), havn't run into many problems besides a small algea bloom here and there.

So I would go ahead and use the dechlorinated tap water for the initial fill.

As for the unit, like everyone else said its really easy to set up. Most of them have adapters and such that you can fit onto the intake to setup with a sink or a laundry line or something. As for removing it, I would say the ease depends on how big the unit is. I have a 4 stage unit and to me, its just hassle to disconnect it from my laundry line and then pick it up(it gets a bit heavy since there's water in it after you use it) and hide it somewhere in a cabinet or something. So I just leave it on my laundry countertop next to the sink. It might not be so bad if you have a smaller unit like a 2 stage or something.