Let me see if I can help you with this. First of all If I am understanding correctly you are trying to find out if the country you will be residing will sell SIM Cards and if they will work on your device. Secondly you want to know if you can sync your iPad with the Apple Store or iCloud? This is how I am understanding your question, Please let me know if I got it right. I will proceed with the following understanding stated.
My iPhone & iPad experience in other countries thus far
I am a USA citizen I was able to use my iPhone 2G throughout China using one of their pre-pay SIM cards. My phone was jailbroken so I was able to make calls anywhere in the country. I was able to do the same in Canada too, actually the USA TMobile SIM card worked in Canada it just was expensive but it worked. I currently live in Canada but I purchased my iPad in the USA. I do not have an iPad that takes a SIM card but i would suspect that if you put a pre-pay SIM card in it will work fine. My thought is that buying a Prepay card is pretty common place and you should not have an issue finding one and using the service.
Regarding Pre-Pay Navigational GPS
I am assuming that you are trying to get the GPS service to work so let me just say that it is very very possible to just download an app and you probably don't even need PrePay... for example I just made a trip to Toronto I downloaded this Toronto App map program... Now on my iPad I DO NOT have wireless service set up with a phone company but somehow and to my HUGE surprise the GPS feature was working and my movements throughout the city were literally working pretty accurately. I wonder if you too may be able to download such an app that will activate the GPS feature on your iPad and allow you to follow your movements in the city... I am assuming this is what you want to do. If not please correct me.
Sync has absolutely nothing what so ever to do with SIM Cards so do not worry about that. All you need is a 3G or some kind of Data service like WIFI or LTE or WiMax to connect to the internet. As long as you have that you will have absolutely no issue with sync. The one thing that I note is that you want to SYNC with your PC at home... well this is not going to be possible seeing how your computer at home either needs to be with you on hand in a LAN environment or directly plugged up into it - i mean if you find some diabolical way to keep it always connected on some kind of cool server then yeah you can connect to your computer at home haha. Anyway instead of trying to connect with your computer at home... get into the practice now of either using iCloud sync which in your case since you will be away will be the wisest course of action... Naturally if you are only concerened about syncing at home well why not just wait til you get home thats another option... but seriously if you are gonna be out of your home country anything can happen to your device on the road so the best thing to do is be able to connect remotely as i stated before using iCLoud... OK i hope this helps let me know if you have any questions or thoughts about whats been posted.