no need to fret. if you hatch it using the default egg incubator, its all ok. remember, you have limited space to keep eggs (and you cannot delete eggs too afaik), and eggs take time to hatch. putting in the time factor and possibility of missed opportunity to get better eggs, i'd say just go for it. hatch'em eggs!

gps connection problem. nothing to worry, and you might even encounter pokemon for "moving" around

the 3x incubator means you can use it to hatch 3 times, then its gone. that one is good if u wanna hatch 5 or 10km eggs. there's a limit of free egg incubator that you get by lvling up. i think 4 or 5 times only. not sure if pokestop gonna drop incubator in the future or not lol