About upgrading. I would say buy CAREFULLY if you're newer to paintball, pre-07' spyders like yours and upgrading them.
Your Rodeo came out when Kingman was using a number of proprietary sizes and fittings that can make upgrading a monumental pain in the ass.
Here's a pic I made to illustrate the most important things:
I guess you could say the barrel thread too, but I don't consider that a big deal at all. just shop for spyder threaded barrels.
Now, of course don't let all this discourage you, once you're aware of all the hidden BS, there's plenty of simple DIY mods and pretty good aftermarket stuff that are 1/2-sometimes a 1/4 of the price they used to be because of the lack there of demand nowadays. Another tip: 90% of the spyder parts on sites like pbgateway.com are a ripoff. Ebay, I&I sports and the buy/sell/trade section of this forum is a much better place to start after you find out what you need/want IMO.
Oh and here's a oldschool pic of mine back in the day.