I've been to Stalag Luft III so can provide lots of information on visiting there.
Zagan (formerly "Sagan") is in the region of Lower Silesia in Poland. I found that the easiest way to get there is from Dresden via train (as I recall, at least 1-3 changes, perhaps in Zgorzelec or Legnica). One important point to note - be sure you have Polish Zloty on hand as the train in Germany will only take you to the first stop in Poland. When you arrive in Zagan, the easiest way to get to the hotel is via Taxi (there will probably be at least one waiting outside). I found that Taxi's were quite inexpensive.
I'd suggest staying in the Hotel Willa Park, which used to be an old hospital in the Soviet era. The rooms aren't luxurious, but they were large, clean and comfortable. The hotel served a great breakfast (which may have been better than usual during my stay, as there was a large wedding party there at the time).
The Museum is located on the site of the former Stalag Luft VIIIC. It's some distance from the hotel, so I'd recommend taking a Taxi. The Museum Curator is very knowledgeable, especially as he's attended a number of reunions with survivors of the camp. There's a recreation of Hut 104, which is where The Great Escape took place from. This website provides more information - https://muzeum.zagan.pl/en/stalag-luft-3/ .
It's easily possible to walk from the Museum to the actual site of Stalag Luft III. The Curator can provide directions. I didn't have any trouble finding the camp. Although the path of "Harry" is clearly marked out, it will take some imagination to envision what the camp looked like when it was in operation. The foundations of "The Cooler" and the Hospital are still there. There are concrete rooms in the basement of the hospital, so pack along a flashlight if you want to venture in there.
If you want to recreate the walk from the exit of "Harry" to the rail station, again it's not a difficult walk, maybe 10-15 minutes. You can go through the woods (as the POW's did), or use the small road that passes by the camp. There's a small building covering a stairway which leads down to the back entrance to the underground passageway to the station. If you want to visit The Memorial to the Fifty, continue past the station entrance towards the main road. Just before the main road, you'll reach a store (grocery, hardware?). Turn right on the small road and go behind the store. The memorial is not too far along that road, across from a Russian cemetery. The remains of "The 50" were re-interred in the Garrison Cemetery in Poznan, but the memorial built by the POW's is still in Zagan.
Regarding the language issue, I found that many of the people I dealt with seemed to be fluent in German (Taxi drivers, etc.), but English was more of a problem. Anyone who says "all the younger people in Europe can speak English" obviously hasn't been to Zagan. I had quite an adventure ordering lunch one day in a small cafeteria, but thanks to some helpful app's on my phone and a bit of pre-study, I muddled through it. I missed the part where the Perogies were priced by weight, but it was a fine meal anyway.
It would be a good idea to become familiar with the details of the escape, so you have some idea what you're looking at. If you're interested, have a look at this website - http://robdavistelford.co.uk/webspace/gt_esc/ . I can recommend some good books also. I did extensive research on this before my trip and I'm currently reading yet another book on the subject. You could also watch The Great Escape movie. One of the surviving POW's who saw the movie said that many things depicted inside the camp were reasonably accurate, but everything that happened outside the camp was pure Hollywood fiction. For example, there was NO dramatic motorcycle chase.
Hope this helps.