I have an 870 that I would like to upgrade.  One of the things I would like to do is have the receiver/receiver tube pakerized.  My question is do I have to worry about that peice of metal on the side (inside) of the receiver that seems to guide the shells?  Does it need to be removed; and if so would I need to send it out to an 870 armorer to remove it or can I do it in house?

That's the ejector assembly.  It can be left in place, as can the shell releases.

Quoted: ...as can the shell releases.

R u sure?  Would the parkerizing get behind them?

Quoted: Quoted: ...as can the shell releases. R u sure?  Would the parkerizing get behind them?

Yes, and unless you really flushed the parts, this section of the receiver would rust from the inside out.

Bottom line is pull the parts, and restake them back in after the parkerizing job.

The two flat springs inside the receiver do not neccesarily have to be removed, but can be without difficulty.
Re-installation is the hard part.
If the burner is sent to someone that routinely phosphates 870,s then you should allow them to remove and re-stake the components.
If you disassemble the shotgun, you might find that you can slide the shell latch (the flatspring on the ejection port side) forward and backward a little. You will note that one of the pushpins will locate the latch upon reassembly. The factory staking prevents this component from falling out upon disassembly.
A special tool is REQUIRED to do this properly, a centerpunch and a hammer are not the correct method.
If the individual doing the phosphating does not have the tools or the experience in this matter, leave them in for phosphating. After the shotgun returns, apply a good dose of oil to all the nooks and crannies of the ENTIRE shotgun, and everything will be OK.
An 870 specialist will not always remove the components, but if the are reputable they will state that they restake properly after removing the components.