The blue waistcoat (vest) is very easy, and I think you could totally do it! Click here.
The other vest is not as easy because of the cable work. There are some foreseeable challenges when you get further into the V-neckline shaping. The decreases will eventually bite too far into the pattern, and you'll have to finesse the cable pattern due to the lack of stitches to perform the entire cable repeat.
This challenge would be a bit of a challenge for me as well. Plus, each side...the left front and the right front...will have a different remedy for the lack of stitches left on the needle to make it look right.