>> I'll be traveling to Murren for a few days next week and have a four day Swiss travel pass. I believe this gives me a discount on the cable car up to the schilthorn. Can someone confirm the round trip cost of this ride with my pass?
Your Swiss Travel Pass entitles you to a 50% discount on the full fare of CHF 82.20 return between Mürren and the Schilthorn, i.e. CHF 41.40.
This, and information about other fares in the Jungfrau Region, can be found here:
www.jungfrau.ch/filead min/Prospekte_und_Bros chueren/Jungfraubahnen _Fahrpreise_Preisliste .pdf
>> Do I need cash for what I owe or is a credit card accepted?
Credit cards are accepted.
>> with the swiss travel pass do I just march up and get in the line to board using the pass as my "ticket", or do I first go to the ticket line and show my pass there?
On trains and buses where travel with the Swiss Travel Pass is free, yes, you can board with just your pass.
Access to cable cars and some mountain trains is usually through a barrier gate, for which an electronic ticket is needed to release the gate, even if you are entitled to free travel (e.g. Stechelberg to Mürren). So in these cases, you need to present your Swiss Travel Pass at the ticket counter to receive a free (or discounted) ticket for the barrier gate. That applies to the Schilthorn too.
Some of the mountain transport will be closed while you are there unfortunately. This includes:
Train Wilderswil to Schynige Platte - anticipated opening date 27 May
Funicular Mürren to Allmendhubel - closed until 15 June inclusive
Gondola Grindelwald Grund to Männlichen - closed until 24 May inclusive
Cable car Wengen to Männlichen - closed until 19 May inclusive
There will still be plenty to do though!