what are the methods/broker types that it's possible to trade interest rates with?
The futures market is the primary way for individual traders to operate in fixed income.
Are interest rates exchange based?
Yes, though not generally as rates per se, but rather at fixed income instruments such as Bonds, Bunds, Gilts, Eurodollars, etc.
Is interest rates trading a regulated market?
Yes, the futures markets are regulated.
How do the stakes work - in terms of position size descriptions?
Each futures market has it's own size definitions, which are pretty readibly available. There are also some mini sized contracts.
How does the potential for profit and loss compare to forex trading?
Depends on the method of trading you use.
How big a market is interest rates trading compared to forex?
Not even close. Forex is bigger than all the other markets combined.
Which are the main/most liquid interest rates to trade?
Eurodollars are the highest volume across the board. You can find liquid trade in instruments based in all the major currencies.
Does trading via just conventional TA work well?
It certainly can.
Is interest rates trading a 24 hour market?
Yes, but not with the same kind of activity you would see in forex.
What do interest rates traders need to look out for that may affect the prices? - the same Economic news releases that affect forex prices?
Most of the same indicators apply. Actually, the fixed income markets tend to be more sensitive to these releases than are forex or equity markets.