Regardless, the advice you receive here will be *very* broad. e.g. there are different types of Achilles issues, i.e. whether it's the sheeth (paratendon) or tendon itself; whether it's 'tendonitis' or 'tendonosis'. So...best get an ultrasound if you really want to know what's going on. A decent physio should have a scanner and shouldn't charge too much.
The Achilles has poor blood supply, therefore DON'T rest it. Try and keep some kind of maintenance running / exercise programme. 'The Achilles hates rest' - this was told to me by a professor of biomechanics. I'm not advocating running your usual mileage. I'm not even advocating running on it. But be assured that the best way to heal it, along with a correct eccentric stretch / strength routine, is to keep it active. Walking, cross-training machine - whatever. Google it - the AT's poor blood supply means it needs gentle exercise.
Secondly, DON'T take Ibuprofen for more than a day or two. Research suggests it weakens tendons in the long run. Inflammation is the body's natural response. By suppressing it with Ibuprofen you're preventing it from reinforcing fibres during the healing process.
Google this stuff - I'm not making it up. Good luck.
BTW - I find avoiding uneven surfaces is best for my AT. Try a few days / weeks on the treadmill and see what that does. The worst thing for me is hard, uneven surfaces.
Realise that, by starting a thread on this, you are opening a massive can of worms... There's little consensus, hence the various techniques such as POSE / Chi etc all disagreeing on some points.
If you adapt to FF strike, realise that the adaptation takes longer for some people. Some people seem to be able to change over in a few months, others get injured. The 10% rule cannot be breached if you change over - i.e. never increase running load by more than 10% in consecutive weeks.
Some common traits which Pose / Chi and Pirie all agree on:
NEVER let your cadence go below 180 strikes p/minute. Elite runners typically are above 190 (and this is relevant to mere mortals, since elites have the largest training loads). Get a metronome if necessary.
If your Sunday run is currently say, 10 miles, when you change over, go down - literally - to 3 miles and build up by 10% p/week. Injury can strike without warning - often when you feel invincible. Be patient and cross-train if you need more cardio.
Calf strengthening is a good move (calf lifts with dumbells). Foot strengthening (Google 'foot gymnastics') is also a good move, as your metatarsals / extensors will not be used to doing so much work.
Whilst I'm not an advocate of one strict discipline, make sure to regularly do drills. Pose drills are useful, as is high-knees, butt kicks etc.
Changing your gait is the biggest single change a runner can ever make. I'd advise taking advice from anyone who says otherwise with a pinch of salt.
Make sure to Google for Gordon Pirie's free book: 'running fast and injury free'. It's a few yrs old, but I've yet to find a mistruth in it... He didn't have the science we have today, but his empirical evidence / experience is difficult, if not impossible to disagree with.