Here are some pictures - I didn't get a picture of the hole but the last picture shows the view top down - I was working bottom-up as Dan at AS tech support said doing it bottom up would be easier. If you look carefully, you'll see the clear tube and clamps - note - the plastic liner on mine is not flat - it's staggered plastic - I drilled my inspection hole on the plastic "bar' to the right of the low point drains, towards rear of trailer, more or less beneath the broken tap - but on my FC 28' 2010 it looks like the hose would be under the portion of the plastic liner that is indented when lookng up - this is NOT where I cut my hole. Post #2 shows a picture of the bottom liner of the trailer and the "Z" pattern of the plastic.
I used a 2 ton bottle jack to raise the trailer so I had more working area - still was tight - lots of crawling back & forth.
Used a cordless drill with a 1/4" bit to drill through the black plastic liner - wrapped some copper wire around bit to act as a stop as i didn't want to drill through the water tank - using a low drill speed and taking my time, i could feel when I went thru the plastic - needed to be careful when I got close to the plastic outlet where the hose attaches too. Once drilled, I used a 3/8" bit to make the holes larger and a Wiss cutter to cut the plastic between the drilled holes - the pile shavings in the picture shows all the waste from holes drilled - a dremel router would have been a clean cut but didn't have my dremel as trailer is far from home.
Once I got the hose exposed, used a long slotted screwdriver to loosen hose clamps but had to coax the clamps by twisting the broken tap with a pliers to get it in the right position (was originally installed before the floor went in so the AS installers put it in top-down.
Felt a lot like doing a tedious surgery - patience paid off. Wound up removing both clamps and removing clear plastic tube - it had plumbers putty stuck in it - not enough but I used a large drill bit to ream it all out I could have bought a new piece of tubing but what i had was still okay ad it would have meant another trip to Home Depot.
Put in the new aluminum tap purchased off Ebay (link above) Seller doesn't sell the drain tap but pointed me to another seller on Ebay who does sell them. Put it all together and used a piece of small sheet metal and several self tapping screws to cover the hole - but now I have an access panel just in case. The sheet metal covers the span of two "outer" bars of the plastic liner and I used the metal strap that holds the water tank as a straightedge to align the plate before screwing it into the plastic. - I did see a metal bar near the water tank (part of the chassis) is a little bent - nothing too serious but it shows I must've hit a rock when we went to Big Bend National Park last December. The only way to straighten it would've been to remove the fresh water tank and I wasn't going there!
A previous post, above shows a link to the aluminum tap replacement - it is an exact replica of the plastic OEM but doesn't have a plastic handle (that will break down the road) and below is a link to the drain tap that fits into the aluminum tap that replaces the plastic one.
1 8" NPT Petcock Drain Valve | eBay
I found Dan at A/S to be a good resource in coaching me through doing this operation - hopefully never again! I believe the dealer charges @ $200 and probably worth it but I felt I could do this if I took my time.