A Return to Mashing: My First All-Grain

I've been determined for a while now to try my hand at mashing again.  After my disastrous previous attempt at doing a mash, I spent a lot of time thinking about what went wrong.  My conclusions were two-fold: 1) I did a horrible job of temperature control; and 2) I have no idea what really went wrong.

I've since attempted a mini-mash with three pounds of left-over grains (the same size as my previous partial mash), and it went pretty well.  I learned a few things, the biggest being that there's a significant temperature differential between the top of the grain and the middle.  In other words, laying my floating thermometer on top of the grain bed won't give me an accurate reading.

Still, given how poorly my first attempt went I don't want my first all-grain to be an expensive or difficult recipe.  I asked around on homebrewtalk.com, and I got a fairly universal response: BierMuncher's Centennial Blonde recipe.  So, I'll be making a 5-gallon batch of this on Wednesday:

BeerSmith's estimation of the color of the Centennial Blonde

Recipe Type: All Grain
Yeast: Nottingham
Yeast Starter: Nope
Additional Yeast or Yeast Starter: Nope
Original Gravity: 1.039
Final Gravity: 1.008
IBU: 21.6
Boiling Time (Minutes): 60-75
Color: 3.9
Primary Fermentation (# of Days & Temp): 4 days at 68 Degrees
Additional Fermentation: Kegged, chilled and Carb'd for one week
Secondary Fermentation (# of Days & Temp): 5 Days at 68 Degrees

Batch Size: 5.50 gal
Boil Size: 6.57 gal
Estimated OG: 1.040 SG
Estimated Color: 3.9 SRM
Estimated IBU: 21.5 IBU
Brewhouse Efficiency: 70.0 %
Boil Time: 60 Minutes

Ingredients:
------------
Amount
7.00 lb Pale Malt (2 Row) US (2.0 SRM)
0.75 lb Cara-Pils/Dextrine (2.0 SRM)
0.50 lb Caramel/Crystal Malt - 10L (10.0 SRM)
0.50 lb Vienna Malt (3.5 SRM)
0.25 oz Centennial [9.50%] (55 min)
0.25 oz Centennial [9.50%] (35 min)
0.25 oz Cascade [7.80%] (20 min)
0.25 oz Cascade [7.80%] (5 min)
1 Pkgs Nottingham (Danstar #-) (Hydrated)

Mash at 150 degrees for 60 minutes.

This will also be my first time attempting to calculate my efficiency (things went so badly last time it wasn't worth the effort).  Wish me luck!