Garden Work........?
Answers:
Just snap your fingers and it will all be better.
OK, since that didn't work...unless you can afford a professional landscape crew to give you a makeover...go get a wheelbarrow, shovels, rakes, water hoses, work gloves, etc. and get to work. If you can't fix everything before your party, you can at least get started and any improvement will help, based on what you wrote.
Start by hauling the rocks and pulling the weeds. If you can afford to have a tree service take care of the stump, most of those guys have stump grinders that will make quick work of the stump by grinding it down to below the level of the ground. If not then go to Home Depot or Lowes etc. and they sell stuff that you can treat the stump with and it will start dissolving it. This method will take a lot longer but will eventually get rid of the thing.
You can put some sod down in the area that you said is a HUGE blotch of dirt. Your garden center can tell you how to prepare the ground for this. And you can put in some cheap flowers to give you some color. Pansies are cheap and you can buy them in full bloom, just be sure to keep the properly watered, again the garden center can give you instructions.
Other answers:
all it takes is money, time and a lot of back breaking hard work to make it look better
all it takes is money, time and a lot of back breaking hard work to make it look better
If you don't have time to plant things and have them grow, look at doing some container plants. Even the stump can be dolled up with planters/pots sitting on it. If guest will be there at night, put some little party lights around the stump as well. Gather up as many rocks as you can and even place them around the stump or design the rocks around to make a walkway or edging. There's lots of ideas available!
Cut or pull the weeds. Get a few attractive potted flowering plants and put them on the stump. Get some flag stones and put then on the huge dirt patch, and put your grill on it. Have the party at night and no one will notice the difference?
This sounds like my yard. ha-ha
If it's clean at least that's a start.
Distract from problem areas with garden whimsy, such as colorful birdhouses or statues. It will keep people from staring at the tree stump. You could also turn the tree stump into a table or seat. Paint it a fun color and put a outdoor cushion on top for a seat, or set a tray on top for a table. Something that was once an eyesore is now fun, functional and a great conversation piece.