Inside:
Insulate ceiling - If in the attic this can be easy as you can add batten insulation or rent a blower and blow in bags of insulation.
Insulate walls - This could be difficult. Some people recommend using foam which always appears to be a pain in the rear to me. What are you exterior/interior walls made of? How old/any plan to replace them?
Insulate floors - Easy if on a crawlspace as you can install battens of insulation and hold them up with thin metal rods called insulation hangers.
Add radiant heat flooring (
http://www.mrmoneymustache.com/2014/02/16/the-radiant-heat-experiment/) - Difficult but doable if on a crawlspace/basement. Personally I am not for it unless you go for it during new construction. Not a lot of ROI usually.
Replace carpet (with hardwood and/or new carpet) - Tearing out old carpet is easy. Putting down hardwood floors is doable. Putting in new carpet is something I have always hired out.
Paint bathroom - easy
Paint interior - easy unless very high ceilings
Replace blinds with better ones - easy
Outside
Burn burn pile - easy, just need to know local regulations and don't do it on windy, dry days
Amend yard soil with topsoil - easy but need more info with regards to the amount you want to add
Fix PH balance in yard soil - buy a soil tester and add sulfur if too low or lime if too high (going from memory here)
Replace tree in front with flowering pear - How big is the tree? How close to something valuable/easily damaged by falling tree
Replace front shrub with Japanese maple - easy, just cut and plant a new one
Remove ugly grassy bushes in front yard - easy
Replace lawn - not a lot of experience here but I did overseed my lawn last fall to put in more clover and rye
Paint exterior - easy but what kind of exterior? Wood in good condition? Or cedar in poor?
Install deck in back yard - May need permits here... How big and recommend calling your local building dept to ask if permit required