Should I replace my battery?

Recently my battery on my galaxy s7 has dramatically dropped to under an hour of battery life. It costs about $70 to replace professionally but my dad just got laid off and while we can certainly afford that it would be smart to try to save money wherever we can. Before I jump off the deep end I have a few questions after seeing the guide for a battery replacement.

1) How hard is it to not break the glass backing off the phone in the process?

2) For a beginner to phone repair how hard I it do to in general?

3) Is it worth the risk?

4) Can the s7 edge or any other oem higher capacity batteries battery fit in the galaxy s7 so I can give a battery life upgrade as well as a repair?

5) Does the phone remain waterproof after the repair?

6) Can you replace the heat gun with a blow dryer?

Thanks for the help