4 lbs of grain should be manageable, so 2 lbs each malted wheat and pilsner malt (both milled). Mix them with 1.5 gallons of ~164 degree water, to make a mash that is ~150 degrees. Try to keep the mash at that temp for around 45 minutes and give it a stir once in awhile. Rinse the grain with a gallon of ~170 degree water to remove more of the sugars (how you do this will depend on your set-up.)
Top off with water to 3.5 gallons total liquid. Take a sample, chill to ~60, and take a gravity reading. You want your concentrated wort to be ~1.071. 1.043 would be 100% efficiency, so if you got 1.030 (for example) you’d have 30/43 = 70% efficiency.
Add extract to get from where you are to the target (1 lb of DME will add .013, 1 lb of Wheat LME will add .011). In my example from above .071-.030 = .041 using DME you’d need .041/.013 = 3.2 lbs or using LME .041/.011 = 3.7 lbs. DME is easier to work with in random amounts, and it stores better so that’s the way I would go (5 lbs should cover you even if you have awful efficiency).
Bring to a boil and let it boil for 15 minutes. Then add about 3 AAU of hops (1 AAU is equal to 1 oz of 3% AA hops) and boil for another 45 minutes. Add ½ tsp of yeast nutrient, and boil for 15 minutes. Chill the wort, then add enough cold water (bottled or boiled/chilled) to get to 5 gallons. Take your original gravity reading. Pitch a pack of WY3068 that smacked a few hours before brewing (a starter would be ideal, but you should be able to get away with a fresh pack).
Hold the fermenter somewhere that is in the high 50s for 10 days (you can let it climb into the mid 60s toward the end to make sure fermentation finishes), and then if you want drop the temp to lager for a week to drop some of the yeast/protein out of solution. Finally use a priming sugar calculator (for example:
http://www.tastybrew.com/calculators/priming.html ) to figure out how much of the sugar of your choice is needed to carbonate the beer to ~3-3.5 volumes of CO2. Mix the sugar with some water, bring to a boil, and mix into the beer.
Hope that helps, good luck.