Replace Boiler replace system

[Amigo4lavida]

A large 30KW oil fired system, about 25 years old. About to replace with gas, condensing boiler. Would it be prudent to rip out the old system and renew all components(existing system working OK, just that oil is too expensive)
Would a good power flush be enough?

TIA

A4l

 

[linkyplumb]

What type of system is going in, sealed or gravity.

I would think at the least, controls need to be upgraded, and fit trvs if not already fitted.
If going sealed from gravity, then there is obviously a potential for pipes,joints etc to leak under pressure.