2 pipe steam Radiator not heating / Traps / System Replace ?

2 pipe steam radiator not heating / trap / system replace ?

I have just purchased a home with a two pipe steam heat system (The main supply and return lines split just after the boiler to feed each side of the house. Also, each individual radiator runs off the main (i.e. it is not connected to another radiator) and has its own return line to the main returns in the basement. I purchased The Lost Art of Steam Heat, while it has given some nice background, it is somewhat over my head.

I have a couple of issues. One radiator on the second floor takes considerably more time than all the others (save one) to heat. The return line on the other side of the trap feels just as hot as the radiator itself once the radiator gets up to full heat. However, by this time the downstairs is extremely hot. The other radiator on the second floor (and this is the first radiator fed off one side of the main from the basement) does not get hot on the bottom at all (It eventually feels like it is warming on the bottom but the rate is slow compared to the top and I am wondering if it is just heat transfer to the metal or water that may be clogging the system). From reading the book I understand that trap failure at the return on each radiator is a common problem. However, in the fall I had new floor installed and four downstairs radiators were disconnected (with the steam supply valves closed and covered) and no steam appeared to be coming from the return side of the radiator which was only taped (as I understand may happen when the traps fail).

1) I am wondering if this is a likely trap failure ? (One failing in the open position and allowing the steam to run, and one in the closed causing the condensation to back up).

2) Is replacing the traps on the two problem radiators the best starting point?

3) Should I replace all the traps at once ?

4) How much should a new trap cost? (I can't find a price online but from similar products I am guessing $60-100)

5) What is the benefit to steam over hot water? Is it more energy efficient to run?

6) Should I convert to hot water ? (if the traps have to be replaced every 4-5 years (as suggested in the book) at 11 radiators @ $100.00 I am looking at $1,100 in traps alone ever 4 years.

7) Can a hot water system use any of the existing steam piping?

8) Should I convert to forced hot air?

9) Which system is the most cost effective to install ?