Solid Hardwood, Engineered and Laminate Flooring - tub or flooring first ?

Help! We have sewage coming up into the yard from a drain pipe (or possibly it is a vent pipe? It is an open white pvc pipe that cocmes up into the front yard near the house). What would cause this? Is it something that can be easily fixed by (very) novice homeowners or are we better off calling a plumber?

Some info that might help in answering my question:
1. We have had alot of rain over the past week
2. We have had a problem in the past with the toilets flushing poorly, but the problem resolved on it own.

Thanks for your help.

I did it ! I have gutted my entire bathroom , the subflooring is down , drywall is hung primered and painted,shower has been installed and working , plumming for toilet and vanity are through the floor . I am ready to start the garden tub , do I want to lay my Pergo flooring before or after putting in said tub ? Thanx DBLT

Pergo last...... Unless, you want the electritian to drop a hickey, the plumber to drop a pipe wrench, a laborer to drop a shovel, a painter to spill his bucket on your brand new floor@#!?& But then you like the expense of flooring under your tub where it cannot be seen and can suffer water damage. Whooooops..... good luck with your project.:)