If I'm not mistaken, if you replace the tank you also have to buy shrouds .
Quoted from KTMster:"The E/XC fuel tank capacity is 2.1 gallons and has separate shrouds. The M/XC fuel tank capacity is 3.5 gallons and the shrouds are part of the gas tank...they actually hold gas." I would be scared of popping those shrouds if they hold gas.
On pricing:
'01 520 MXC - MSRP $7,148
'01 520 SX - MSRP $6,698
'01 520 EXC - MSRP $7,248
'01 400 EXC - MSRP $6,998
'01 400 MXC - MSRP $6,898
'01 400 SX - MSRP $6,448
About four hours from you is Wilson's Motorcycles in Fresno. If there isn't another KTM dealer near you call them to compare.
(Spam note: don't go there)