Doug, I'm not sure where North Dighton is, so I can't tell you where to look for local matches. Check in the back of the Outdoor Message (the GOAL newsletter - you ARE a member of GOAL if N. Dighton is in MA, right??).
As for what you need:
Reliable centerfire pistol at least 9mm or .38 Special or larger.
Concealment holster for your strong side (no cross-draw, small of back, shoulder holster or Thunderwear/Smartcarry allowed for safety reasons.
Concealment garment (a vest is fine).
At LEAST 2 spare mags or speedloaders - more is preferable.
At least 200 rounds per match/practice.
The usual safety gear - eyes and ears.
Good luck; IDPA is a ton of fun.
(As long as your Sigma shoots RELIABLY - no jamming - it's fine.)