These are the costs I know of with trusts:
1. The legal costs of working with an attorney to write up the trust language, either in the will, or a trust document, or whatever. This is probably $500-$2000 depending on where you live and how complicated the trust is, but since your Dad has already passed away it sounds like this shouldn't be an issue.
2. Trust taxes. Trusts are their own entity and have to file annual tax returns and pay income taxes just like individuals and corporations do. Costs here are the trust income taxes themselves plus any tax preparation costs.
My parents have an A/B bypass or credit shelter trust. The assets are at Vanguard in a trust account. Vanguard doesn't charge any sort of fee for the account other than the standard expense ratios of the mutual funds in there. Definitely not 1%. The tax prep will be a few hundred dollars, but it is simple enough I could do it myself if my Dad didn't prefer to pay his personal CPA to do both is individual tax returns and the trust tax returns.
Trust income taxes are a thing you'll need to look into. Basically trusts pay income taxes at graduated rates just like individuals, except the dollar amounts for the brackets are much smaller. Distributed income is basically treated like a pass through, so it is taxed to the beneficiary at their rates. What we're doing is distributing enough of the income from the trust to the beneficiaries each year so that taxes are minimized between the trust and the beneficiaries. Look at form 1041 and the related instructions.
You'll need a tax ID number for the trust, which you can get from the IRS for free by filling out a form.
You can open a Vanguard trust account with the tax ID and the trust paperwork and a Vanguard form that is maybe 6 pages long or so.
I would follow the terms of the will exactly - as executor that's what you're supposed to do. Yes, there is TEDRA, which is what I think bobechs is referring to - but to do that you'll have to pay another thousand or two to a lawyer to write up a TEDRA agreement, get it signed by everyone (your Mom and your siblings and you) and then file it with the probate court. It will certainly cost you more to do TEDRA than to do a trust for a few years.