My metal working is not great but if I don't find anything I will give it a try.
Its a good one to start with. Its not too bad. Do you have an angle grinder or a dremmel?
The trick to getting a straight edge is to stick the template to the metal, then clamp a big thick bit of scrap metal to the small part you're working on lined up with the edge you're cutting. Your tools will easily remove the part you're working on, but will take much more time to grind away the big scrap. Once you're close to the target line, you can quickly move the tool up and down using the scrap as a straight edge guide and get a really clean line on your part.
When drilling holes, use a centre punch first so the drill doesn't wander. You can do this using the paper template. Mark the centres of holes in the drawing.
Drill holes slightly over-size to give yourself a little tollerance.