No need for AE, Vegas will cope quite well with this though not quite as easily as using motion tracking.
Stick your background video on track 2
Stick your face on track 1
Open the Pan/Crop window on your face abd check the box at the bottom labelled "mask"
Now use the Bezier mask tools to draw around your face.
Move forward a few frames and move the mask
etc etc.
It's fairly time consuming and the mask controls take some getting used to, but it can be done.
I recently used this technique to have 4 versions of my daughter appear in the same video - these were moving images rather than stills so somewhat more complex, but the result was pretty good (projected onto a screen at the back of a hall - it doesn't stand up to being examined on pause on a TV screen!)

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Tim