The easiest way to learn how to install a bathtub is to take a class at your local home improvement store. These stores sell everything you need to renovate a bathroom and often offer classes in basic plumbing and electrical work, as well as installing various types of appliances and fixtures. You will probably purchase your supplies at one of these stores anyway, so you might as well take advantage of their free classes.
Whether you are upgrading the entire bathroom or just the tub and shower, this will most likely be a good investment. Homes with updated or upgraded baths tend to sell for a bit more since people like a nice bathroom.
There are different models of bathtubs. The type you choose may depend on your available space or budget. If your new tub and shower enclosure need to be the same size as the old one, you will be limited to models that fit into that area.
If you are enlarging the bathroom or moving the tub and or shower, you have more options. If you want a tub in a certain shape, you will probably do best choosing an acrylic tub. These tubs are very durable and will usually last a long time. You can also get them with built-in jets so the tub can pull double duty as a spa.
Cast iron tubs are also very nice, but they are heavy and will usually have to be used in a bathroom with plenty of space. There are modern versions of the old clawfoot tubs which look very nice in the middle of the bathing area. The shower is then separate and can be placed in a corner or against the back wall as a walk-through model.
When you know how to install a bathtub, it certainly gives you more renovation options. Doing this project yourself will save you money which you can always use to buy a nicer tub.