Runnin MTH PS3 on Lionel traditional 027/042 track and switches

10 amps may be a bit high for the breakers. I think many here use something like a 5 to 7 amp (or so) breaker with their old post war transformers. IMO, a good fast breaker is well worth the money. I use PSX-AC's on my layout which are fairly expensive (around $50 each), but no where near the cost of replacing the electronics in just one engine (around $200 DIY, more if you need a tech to do it for you). All I have is command control engines and the extra protection is well worth it to me.  

You may also want to add surge protection to your layout by using some TVS diodes around the layout. A very good idea as well. The one used by most folks here is a 1.5KE36CA, available from Digi-Key or Mouser. Digi-Key has better shipping prices on small orders. For more information do a search here for TVS, there have been many, many good discussions about using them, where to put them and other information. Also, these discussions were by folks a lot more knowledgeable than me.