Heating Help

Replacing expansion tank

I have a gas-fired Vitodens 200 for radiant floor heating and DHW.  It was installed 4 years ago and the expansion tank has sprung a leak, actually several pinhole leaks from internal corrosion.  The tank is an Amtrol model 30.  I have little confidence in the installer, and for that reason and to save some $$ would prefer to do it myself.  It's very hard to get competent technicians here in New Mexico.  I am considering using an Amtrol Extrol RX-30 as it has a plastic liner for corrosion resistance and is said to be designed for high efficiency radiant systems.  My question is, what is the procedure for replacing the tank?  It would appear that one would shut off the boiler, shut off the water, unscrew that old tank, screw on the new tank with some teflon tape... and then what?  Is it just a matter of turning on the water and opening up the manual air bleed valve at the top of the unit until all the air seems purged?  Any help would be appreciated.  I have some mechanical skills but would not hesitate to hire help if I think it's needed.
thanks much
Bob

Expansion Tank

Shut off the water to the system , shut off any isolation valves to heating zones , attach hose to boiler drain or drain valve that is not isolated from the tank . Adjust air charge of new expansion tank to match normal system charge .. Prepare tank with pipe dope .. Drop system water pressure ..Remove old tank with a 7/8" open end wrench . Expect ruptured tank to be weighed with water ..Spin on new tank ... Tank should be hanging down and wet , tap up .. Tank up can catch air and rust out ....

My concern why so much rot... Was a oxogen barrier pex used ?

Read installation instructions

Check installation and replacement instructions from the manufacturer. Most of them available on manufacturers web-sites. If not, call them.