That's quite a picture you have there. It looks like the end of a dryer vent. The only sure way to tell if it's clogged is to run a brush through it from end to end. Do you know where the other end exits the home? Hopefully, it's a short run. Lengthy runs can kill the efficiency of a dryer since it can't effectively move the heated moist air out of the machine.

Whether you need an elbow of a piece of flexible connector depends on where the exit vent of your dryer is relative to the connector end at your wall. Once again, short and smooth for good air flow is better, but you don't always get a great choice here.

Hot and cold water hookup hoses can be purchased. The drain line has always been a part of the washers I've owned. The power line you'll need depends on the type of washer/dryer you have and the configuration of your wall outlet.

There are two types of machines you may be calling "stacked." There are normal, full sized front loading washers and dryers that may be stacked on top of each other and there are one-piece units, usually much smaller units, that are permanently attached to each other vertically. Often, the latter type is called a laundry center.

You'll need to measure carefully to determine your options.