You can contact any decent upholstery shop and get a first rate job. Making cushions is making cushions. You just need to research
the materials. The folks re covering the living room sofa can deal with the problems you will have but they may not know the marine
materials that will hold up all that well. Some of the Sunbrella weave patterns are quite rich looking and are not like the cockpit canvas
. That would be a poor choice since you can get nice fabrics in that price
range that do look first rate. They cost about the same too but might be higher. Expect to pay no less than $30 / yard but they get up over $100 pretty quick. Anything that has "natural fibers" is bad. Check the fabric
for "double rub count" to tell how well it will hold up. Recently the high oil
prices have driven the foam prices sky high. The foam you have may be possible to enhance or may be shot. The really nice cushions have multiple layers with a top layer of memory foam. There is no reason that you can't get the most comfortable cushion that you have ever sat on.
If you don't know how to sew then buying
a Sailright machine is a mistake. It takes skill to do a professional job.