If you are really considering a airless sprayer, look for a unit that uses a siphon tube that goes directly into a gallon of paint with a 50' hose. At the end of the day youll be glad you did. If the Wagner unit is the one I think it is, then its only a quart+ cup gun. Believe me at the end of an hour your arm will feel as though it is going to fall off from the weight of the unit plus the weight of the material, thats why I say to look for the siphon configuration. Secondly you shouldnt have to thin the paint using the siphon unit whereas you will with the cup gun type. Thirdly that cup unit has an extremely loud buzzer sound every time you pull the trigger, and fourthly the type of tips required in that unit will constantly clog up. After a couple of times of stopping to clean the tip will make you want to throw it in the garbage can.
I dont know what your budget is, but it goes back to the old saying, YOU GET WHAT YOU PAY FOR. A respectable unit will start at around $400 and go up from there. If thats out of your budget then you might want to consider the old brush and roller routine. Graco, Titan and Spraytech are some names to look for. I dont mean to sound sarcastic but an airless unit that will serve your needs in not something that youll find in the store below $400. You should also look for a unit that utilizes a reverse-a-tip spray tip. If you should get a clog in the tip, you just rotate the tip and pull the trigger and the clog is blown out. These may seem like unnecessary features to you, but will pay for themselves during a day of painting. Otherwise youre just wasting your money. The Wagner 317E Power Painter might be good for shutters, but certainly NOT walls. Thats not what it was designed for.
If you should be lucky enough to find a good used unit, be very careful to spray some thinner through it first before you hand over your money. Airless units must be meticulously cleaned after each use.
You also asked about Sears spray guns. At one time Sears sold a good spray gun line, they were made by Thomas. Since then they are made in Taiwan or some other Asian country and theyre nothing like the original models. If you are still looking for a Sears spray gun, then look it up online and read the specifications and the CFM it requires. You compressor sounds like its about a 2 horse power unit and my not be able to handle every type of spray gun.
This is a clip from another forum site. If this it the unit your are looking at, you might want to consider a different unit.
I recently purchased a Wagner Power Painter model 317E (110 Watts).
I've run about three gallons through it so far (all latex, but
thinned appropriately). It's been extremely frustrating to use,
though, as the piston seizes in the cylinder every five minutes
or so and I have to disassemble and clean the unit to get it running
again.
I clean the unit very well after each use, and have put it away
oiled and ready to go each time. I've tried the 1.5 quart paint
container and the larger backpack, but get the same seizing behavior
with both.
I've heard that the piston will seize if the sprayer encounters air
bubbles in the paint, but I've been careful to stir the paint gently
and keep the paint level well above the suction tube.
Hope this helps, Id be interested to know what you decide.
Steve