The exhaust replacement is not a big deal at all if you have basic tools. The bike will run better, sound better, and run a bit cooler. Don't expect miracles on the heat though...these 110" motors are just hot running when it gets hot outside.
I hate to even mention this, but sometimes a better oil will help the noises on the top in a little...again, don't expect too much, but some improvement. If you're not already doing so, I'd recommend putting task specific fluids in the tranny, primary, and crankcase. A lot of folks here use Redline products, and that is what I personally prefer as well, particularly the Redline Shockproof for the transmission...it makes a difference in shifting, finding neutral, etc.
You can find their products here:
http://www.racerpartswholesale.com/product/RedLineOilBigTwin20W50Powerpack/Motorcycle_Oil_PowerpacksYou'll need to add one more quart of primary oil if you get the PowerPack Kit...the funnel is handy, and you get a hat...

It's good stuff...there's other good stuff too, but it's hard to beat their transmission oil, so I'd at least get that. Mobil 1 Vtwin is good for the motor and easier to find, but I just order the Redline stuff and be done with it.