Oil change kit
 

I just bought the oil change kit. Before I install it would it be better to drain the oil out to avoid a mess?

Not necessary to drain the oil first. The 3/4" plug you're replacing is above the oil level in the crankcase so no muss, no fuss.

edit: Huge hint - a 3/4" 12 point socket fits the square head on the plug perfectly, much preferred over vise grips, channel locks or any other shade tree method you're tempted to use. There's a straight shot to it with an extension without removing the carburetor too.

I want to add this, but I am already using that plug as the oil return line for my filter. I think I would need a Y-valve to switch between filter and oil change.

I have this exact arrangement and it works out great.

Thanks guys
 

Now I have installed the kit. Here is my question. I have a west marine manual oil vacuum. Don’t I need a fitting on those tubes to attached to the 1/8 male pipe that is capped?

I don't know what tubing is connected to your oil removal pump, but in general, Moyer's oil change kit comes with barbed fittings to connect the drain tubing with your pump tubing, and a cap to cap off the drain tubing. If the included barbed fitting is not the right size for your vacuum pump, just take your pump and the supplied fittings to a hardware and see if they can fit something up. Some of those pumps have a thin long tube that's meant to go down the dipstick tubing, in which case You may need to change out the hose on the pump, or splice a different sized hose onto the pump hose (using barbed fittings) if you can't find appropriate adapters. Get brass, not plastic.

In my case, the vacuum oil changer (a globe shaped affair), came with a clear plastic hose that the thin dipstick tube slid into. I removed the dipstick tube and found that, by sheer good luck, the OD of the clear plastic tube was an exact match for the ID of the oil hose I was using. I was able to put a short piece of oil hose on the Y valve's barb, and plug it when not in use.

To use, I just remove the plug, insert the vacuum's hose into the oil hose stub, open the Y valve and pump away.