yes, if you format it, it would wipe the HD
you can use software for reading/ writing to "PC" format (meaning NTFS format)
use the program called PARAGON or TUXERA
as if a "translator" for read/write data from your Mac to the "PC formatted" HD.
however just consider also getting another HD, you need 2 anyway for data backup redundancy.
The single biggest error people make is feeling safe with ONE external data backup, and thats always a terrible error people make.
HD are cheap as dirt. Just format the new HD in MAC OSX extended journaled.
and use the application(s) above to read and transfer the data from your "PC formatted" HD.
Forget about lightning connection HD, USB3 are plenty fast enough, and all HD are limited by spindle speed and spin-ups.
Microsoft OS works find on Macs , whoever told you that , told you another fib.
However Id prefer to run Win7 rather than Win8 on a Mac, but both will work fine.
Being a HD "collector" of sorts, and investigator of them in great detail, here's your best choice on HIGHEST quality HD to purchase:
huge storage, low cost, high quality, very small and portable.
BEST FOR THE COST, Toshiba "tiny giant" 15mm thick 2TB drive (have several of them, lots of storage in tiny package) $100
http://www.amazon.com/Toshiba-Canvio-Connect-Portable-HDTC720XK3C1/dp/B00CGUMS48 /ref=sr_1_3?ie=UTF8&qid=1390020791&sr=8-3&keywords=toshiba+2tb
best options for the price, and high quality HD:
Quality 1TB drives are $50 per TB on 3.5" or $65 per TB on 2.5"
Perfect 1TB for $68
http://www.amazon.com/Toshiba-Canvio-Portable-Hard-Drive/dp/B005J7YA3W/ref=sr_1_ 1?ie=UTF8&qid=1379452568&sr=8-1&keywords=1tb+toshiba
Nice 500gig for $50. ultraslim perfect for use with a notebook
http://www.amazon.com/Toshiba-Canvio-Portable-External-Drive/dp/B009F1CXI2/ref=s r_1_1?s=electronics&ie=UTF8&qid=1377642728&sr=1-1&keywords=toshiba+slim+500gb
*This one is the BEST portable external HD available that money can buy:
HGST Touro Mobile 1TB USB 3.0 External Hard Drive $88
http://www.amazon.com/HGST-Mobile-Portable-External-0S03559/dp/B009GE6JI8/ref=sr _1_1?ie=UTF8&qid=1383238934&sr=8-1&keywords=HGST+Touro+Mobile+Pro+1TB+USB+3.0+7 2 00+RPM
Most storage experts agree on the Hitachi 2.5"
Hitachi is the winner in hard drive reliability survey:
Hitachi manufacturers the safest and most reliable hard drives, according to the Storelab study. Of the hundreds of Hitachi hard drives received, not a single one had failed due to manufacturing or design errors. Adding the highest average lifespans and the best relationship between failures and market share, Hitachi can be regarded as the winner.