I can help Bill !! Sure do wish I had video Skype right about now.... but here goes with my attempt at describing how to get you there without a lot of complicated jibberish.
We are assuming you use the "common" G fingering with your Index, Middle, Ring fingers, so we'll start there with the G chord (give it a strum). Now lift your I & M fingers leaving the R still on the e string 3rd fret, slide your R to the 2nd fret and place your I & M into position for the D7 chord (strum). As you see you can reduce the number of finger movements to only two + a slide and that one "keeps" your place in the string "stack" making it easier to change between those two chords without having to look and verify if you have the correct strings fretted.
Now let's get you to that (dreaded) B7..... We will be using the D7 shape we just did and moving it vertically towards the Bass Tones one string at a time. Make your D7 as above, lift all three fingers (while keeping that shape and move up one string so your I is on the G string (strum). That chord is the AMaj7 (also referred sometimes as C#m7 as an inversion). Move that D7 shape again up one string so the I is on the D string, and add your Pinky on the e string (high e) at the 2nd fret (strum). Voila the B7 in the first position !!
What I always found was getting that darn Pinky involved was a pain. Firstly it has no strength, and secondly these hands have taken a beating over time and don't want to cooperate. I started changing the fingers used for the G to M R P and now switch between sets of fingers depending on what chord I'm coming from or going to.... takes time.
Have Fun !!