I have  1991-a1 with who knows how many rounds through it. The plunger staking has weakened and the only thing to hold it in anymore is the wood grips.  If I put my Packmayer grips on the gun, the plunger pops out.  I have replaced this gun with a new 1911 for duty use. I have the part to replace. It looks like the only way to get this done is to use a $35+ tool?  Is there another way to get this done?  

This will likely be only amone time use tool for me, so it's seems kind of a waste to buy it if I don't have to. I can put ar15's together so this SEEMS like it should be pretty simple.

Thanks.

Get the tool or pay someone that has the tool.

Sometimes you just have to have the correct tool to do the job.
Due to the location inside the mag well no normal punch can do it.
People figure there has to be a cheaper way of doing it, then are upset when the tube comes loose later, sometimes at an embarrassing moment.

Brownell's sell one tool for about $25.00.
Years ago there used to be cheaper tools around but they didn't work all that well and were discontinued.

One way to make the job stronger and pretty much eliminate any chance of the tube ever coming loose again is to use a Dremel carbide ball cutter to make slight countersinks on the tube holes inside the mag well.
The countersinks will give the tubes room to flare out below the surface of the mag well.
This will increase the strength and holding power of the flare, and prevent any interference with the magazine.

You might ask on the gun forums if someone would rent you a tool.

Another option is one of the plunger tubes that mounts with screws or over the upper grip screw bushing.
Kinda cheesy but they seem to work.
If you're going with a standard tube, don't cheat on the price.  Buy a top quality machined from bar stock tube, and make sure that where the mounting tubes meet the main tube are radiused.
This will prevent the tube from breaking off.

Thanks for the information. I bought the Wilson Combat plunger. I will order the tool.  Due to my rural location, it's probably cheaper to get the tool delivered here rather than get it to a Smith. I think he quoted me a price before, and it was in the neighborhood of $50 to do the work.  I also have a new rear sight for the gun and I have recently changed all the springs so after this it should be gtg.