The problem with old radio gear is that the standards regarding channel bandwidth have changed over the years. An older outfit might not play well with somebody else's outfit in the same band. But basic modern gear is now low priced enough that it is very much worth considering. When you can get a multi channel 2.4GHz receiver for less than the cost of a pair of crystals for a 27MHz outfit, the new looks very attractive.
If the batteries are original, they will almost certainly need replacement. An RTR is usually built down to a price, your own build will more likely be built up to a quality that you decide, and if you build it from parts that you sourced, you will know where to get spares from, should the need arise. In your list of parts, add the motor coupler - you need something to connect motor and shaft.