Receiver LiPo packs usually have a C rating of 5 or 10. A 10C 3000mah pack would provide 30amps of current safely.
As stated you would need to find out the specs for the servos to calculate the amp requirements and also the voltage limits. If they can handle around 9 volts then you won't need a regulator for them. Also to use a LiPo on an ignition you would need a regulator to drop it down to 4.8 or 6 volts.
I replaced failing Nixx packs with LiPo packs and regulators , Now I use LiFe and A123 packs as some servos and ignitions can handle the lower voltage from a LiFe pack without regulators.
On one of my 60 size planes with a gasser engine using standard servos, I run a seperate LiFe pack for the receiver and the ignition...2000 and 1500mah. I can fly (5) 30 minute flights before recharging.