As has been said, as long as the transmitter is narrow band, post 1991, then it should be fine for learning on. AM radio equipment is pretty much obsolete and few people have any interest in buying one, so it's value is negligible, but as I said it may work fine to start out with.

I just did a quick search and found that the Sierra is a discontinued kit, but it is a trainer, so I'd say go for it if you're confident in the condition of the equipment. Again, new batteries are pretty much mandatory.

Good luck,
Dennis-