Re: new chain guide?
We use them on production line equipment where I work. They do the job but I feel they're not necessary on our bikes. A well attached and aligned chain tensioner with a skateboard wheel or a bearing mounted nylon pully will suffice and give you many, many miles of trouble free service. The pictured guides are designed for extreme long life, I'm talking thousands of hours of use, and really just too much for our purposes. They're also expensive.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"