A new Delta shower valve could last as long as the last one. They have all sorts of finishes available and different handles or knobs. A new one would have the federally mandated anti-scald technology in it. Many of the new finishes are guaranteed for life, so if they do end up looking crappy, they'll send you new ones. There is some discussion as to whether the stuff in the big box stores is identical to that you buy from a plumbing supply house. First, the rough-in valve is often sold separately in the supply house, then you choose your trim. In the big box stores, they're prepackaged, often with showerhead and maybe a spout. So, if you do go to a plumbing supply house (or order online), you have the choice of geting just what you want, rather than the 'package'. Course, a package is pretty much guaranteed to work as a package...buying bits, you have to be smart enough to read and understand what works with what.
If you're going to tile things, you may want to check out www.johnbridge.com. They helped me a lot when I was doing my last remodels.
As to whether you should do this yourself or not, I have no way of knowing your skill level or what tools you have. Many people do this sort of thing themselves, and some of those end up with a pro trying to make it right - often costing more than if they did it all. But, it isn't rocket science, but a plumber does go to school and practice a long time for a reason...they get it done faster and right the first time (generally!?). You may not. Depends on your tolerance level to frustration and ability to learn new things.