The engine is probably ok. A little alcohol, or even fuel, will help desolve what is most likely gummed up castor oil. Clean it out good, bake it in the oven at 250-300 degrees to help evaporate the alcohol and then lube it up with a light machine oil. Bear in mind that a .40 engine is a bit of an awkward size. It's a bit small for many of the planes in the 40 range. And it's too heavy to use in most 25 size planes. However, it will work ok on a trainer, and slow flying types of planes. Just don't expect to do 3D with it.

The only way to evaluate the plane is to see it, which you've done. If it looks well made, it should be ok. Check for common mistakes like the vertical and horzontal tail surfaces being square. Since this is just a trainer, absolute perfection is not required. However, you don't want something falling off in flight.

On to the radio... How old is it? If it was made post 1991, it is probably ok. The issue with pre-1991 radios, actually a little older than that, but in that vintage, is that they were not narrow band. All non-narrow band transmitters needed to be converted by an authorized service shop or taken out of service by 1991. The Futaba web site has a FAQ that explains this and tells you which models were originally narrow band, which could be updated, and which could not be made narrow band. If the radio is more than a few years old, it may need new batteries. If this is the case, plan on spending $25-50 for them. You might also want to send it to a service shop to have them check it over for proper operation. This would cost more $$$. Make sure you get the charger.

Bottom line, if the radio is fairly new, and the plane is built well, it's probably worth buying. A similar setup bought new would cost somewhere between $250 and $400, depending on which models you choose.