Ball bearing engines are generally more durable than bushed engines and also a little more expensive. You will probably get quite a few replies recommending the Thunder Tiger ball bearing .46 or the Magnum XL .46 or the Evolution .46. I don't own any of them, but understand that they are all good engines and reasonably priced. The OS .46 AX is also a good ball bearing engine, but more expensive. Other ball bearing .46s include the Tower Hobbies and GMS engines. Some people have had good luck with these engines, while others have had problems. I have an OS .46 LA, which is a cheap bushing engine. It runs great but is low on power. You can probably do better for not much more.

I would recommend getting an ARF trainer, which you should be able to find for $60 to $120, one of the good BB .46 engines and either a 4 channel radio or an inexpensive computer radio, such as the Futaba 6EXA. Before you buy a radio, check with your clubs instructors to see what they recommend.

As someone else said, your car servos could be reused, but whatever radio system you purchase will come with 4 standard servos. I would use them in your trainer and save the car servos for a later project.

-Scott