Hi Richard, I have just completed Malta marathon after not running from Dec 12 until the end of Jan due to my Mother passing. I have run several marathons so mentally I know what to expect and managed to squeeze a 18.5 and 20 mile run in just a couple of weeks before the race. I actually felt ok during the race in tough windy conditions only missing out on a pb by just over 1 minute finishing in 3.45.
I also ran the Berlin marathon in 2014 with my one long run being just 16 miles due to a calf injury and didn't actually run for 2 weeks before the race to give my calf the best possible chance of recovery and although the last few miles were tough i finished no problem.
I had a similar injury while training for Berlin in 2014 and only managed 1 16 mile run before the race, after visiting my sports therapist she asked to see my shoes and I had actually only changed to a different brand before Berlin and when she compared them to my old ones she recommended I bin the new ones which I did and never been bothered again.
I've had my hip shaved and smoothed although I cant remember the Consultant mentioning resurfacing, in total I've had 7 hip operations. My last one (shaved) being 5 years ago and after this I decided to train for a 10K just to get my fitness back. I have now run several Marathons my last being Malta last week and have done a few Ultras and touch wood so far no issues.
I will be doing London again this year and hoping for a sub 3.40, so if this is an option for your uncle id highly recommend it.
I did my first 10K in September 2011 just as a way of getting fit after major hip surgery and loved the atmosphere that much i decided to do a marathon so went home that night and entered Edinburgh for May 2012. while traing for this i managed to do the liverpool half in 1.49, so set myself a target of 4 hours for the marathon, i managed to keep to my plan right up to the 21 mile and due to the heat that day really slowed but still very happy with my time of 4.12. Again i loved it and was determained to beat 4 hours so did it again this year in 3.52. which was far easier than my first one have since done the Berlin marathon and managed 3.55 and this was after not being able to run for 3 weeks before the race due to injury.
So to answer your question yes you should be able to step up no problem and if you put the training in it will be an enjoyable experience, i would highly recommend Edinburgh