The game isn't that much more difficult than The Forgotten Sands, but far more time consuming, as you'll need to do three full playthroughs, one on each difficulty mode. Farming for Sand Credits can also be a bit of a grind. And, during one of your three playthroughs, you'll need to complete the game without dying.

Overall, not very difficult, just time consuming. Expect around 20-25 hours to complete.

Each of the three trophies related to completing the game on a different difficulty mode are NOT stackable, which is why you'll need to perform three full playthroughs. To make life easier, we recommend focusing on specific trophies during each playthrough, rather than all of them at once.

First, we suggest playing first on Hard mode. During this playthrough, try to get the Healthy trophy, which involves collecting all the life upgrades, as this of course will also help you on your run through Hard. And, work on getting the Silent Prince trophy, which is getting 50 kills with a speed kill. These silent take-downs will make your run on Hard easier.

After completing the game on hard, reload your Hard game and replay the ending, which will give you 700 credits each time. Once you reach 10,000 credits, you'll unlock the Sand Collector trophy.

Next, start your second playthrough on Normal, and this time focus on getting all the remaining trophies, except for Sand Snake. These might involve the miscellaneous kill-related trophies, and sealing all the sand portals for the Sealed Portals trophy.

Last, start your playthrough on Easy. The only trophy you should be missing, other than Mortal, is the Sand Snake trophy, which involves playthrough through without dying. Hopefully, after two playthroughs on the harder modes, this shouldn't be too difficult. Remember to save often, and reload whenever needed.

VampireHorde has a text-based Walkthrough here:
http://www.ign.com/faqs/2006/prince-of-persia-classic-trilogy-hd-809005-walkthrough-673546

And a text-based Walkthrough by Karma_Hunter:
http://www.gamefaqs.com/gamecube/927617-prince-of-persia-the-two-thrones/faqs/40260

Cheattaro has a great Trophy Guide here:
http://www.playstationtrophies.org/game/prince-of-persia-the-two-thrones/guide/

And a great Trophy Guide here, by Faust:
http://ps3trophies.com/forums/showwiki.php?title=PS3-Trophy-Guides:Prince-of-Persia:-The-Two-Thrones-Trophy-Guide

And stargate55555 has a useful Trophy Guide here:
http://forums.ubi.com/showthread.php/701017-Prince-of-Persia-The-Two-Thrones-Trophy-Guide-amp-Roadmap-Forums

And a Trophy Guide by Platisfaction:
http://psnprofiles.com/guide/894-Prince-of-Persia-The-Two-Thrones-Trophy-Guide

And a useful Trophy Guide on CheatCodeCentral:
http://www.cheatcc.com/ps3/princeofpersiathetwothronescheatscodes.html

A Collectibles Guide by LordMaceX:
http://www.playstationtrophies.org/forum/prince-of-persia-the-two-thrones/197632-prince-persia-two-thrones-collectibles-guide.html

Finally, here's a basic Trophy List:
http://psnprofiles.com/trophies/511-Prince-of-Persia-The-Two-Thrones